# Database Manual - (manual) (Part 7 of 10)

> This part of the MongoDB reference continues the aggregation pipeline operators reference.

- [$maxN (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/maxN-array-element.md): Retrieve the largest `n` values from an array using the `$maxN` operator in MongoDB aggregation.
- [$maxN (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/maxN.md): Use `$maxN` to aggregate the maximum `n` values within a group, filtering out null and missing values, and compare it with `$topN` for sorting needs.
- [$median (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/median.md): Calculate the median using the `$median` operator in MongoDB aggregation stages, supporting approximate methods for large data sets.
- [$merge (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/merge.md): Learn how to use the $merge aggregation stage to write pipeline results to a specified collection, with options for handling matched and unmatched documents.
- [$mergeObjects (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/mergeObjects.md): Combine multiple documents into a single document using the `$mergeObjects` operator in various aggregation stages like `$group` and `$replaceRoot`.
- [$meta (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/meta.md): Explore the `$meta` operator in MongoDB for accessing document metadata like `textScore` and `indexKey` during aggregation and find operations.
- [$millisecond (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/millisecond.md): Retrieve the millisecond portion of a date using the `$millisecond` operator in MongoDB aggregation.
- [$min (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/min.md): Discover how to use the `$min` operator in various aggregation stages to find the minimum value in MongoDB collections.
- [$minMaxScaler (Window Function) (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/minMaxScaler.md): Explore how to use the `$minMaxScaler` operator in MongoDB to normalize a numeric expression within a window of values.
- [$minN (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/minN-array-element.md): Retrieve the smallest `n` values from an array using the `$minN` operator in MongoDB aggregation.
- [$minN (aggregation accumulator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/minN.md): Use `$minN` to aggregate the minimum `n` values within a group, filtering out null and missing values, with dynamic `n` based on group keys.
- [$minute (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/minute.md): Retrieve the minute portion of a date using the `$minute` aggregation operator in MongoDB.
- [$mod (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/mod.md): Use the `$mod` operator in MongoDB to divide numbers and return the remainder, with examples demonstrating its syntax and behavior.
- [$month (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/month.md): Use the `$month` operator in MongoDB to extract the month from a date expression, with optional timezone support.
- [$multiply (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/multiply.md): Multiply numbers using the `$multiply` operator in MongoDB aggregation to compute results from expressions resolving to numbers.
- [$ne (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/ne.md): Compare two values using the `$ne` operator in MongoDB aggregation to check if they are not equivalent.
- [$not (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/not.md): Evaluate boolean expressions with the `$not` operator in MongoDB aggregation to return the opposite boolean value.
- [$objectToArray (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/objectToArray.md): Convert a document to an array using `$objectToArray` in MongoDB, transforming each field/value pair into a document with `k` and `v` fields.
- [$or (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/or.md): Evaluate expressions using the `$or` operator in MongoDB aggregation to return `true` if any condition is met, handling errors and optimizing queries.
- [$out (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/out.md): Use the `$out` stage in MongoDB's aggregation pipeline to write results to a collection, supporting output to different databases and time series collections.
- [$percentile (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/percentile.md): Calculate percentile values using the `$percentile` operator in MongoDB aggregation stages like `$group`, `$project`, and `$setWindowFields`.
- [$planCacheStats](https://www.mongodb.com/docs/manual/reference/operator/aggregation/planCacheStats.md): Retrieve plan cache information for a collection using the `$planCacheStats` aggregation stage, which must be the first stage in the pipeline.
- [$pow (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/pow.md): Calculate the power of a number using the `$pow` operator in MongoDB aggregation, handling mixed input types and overflow scenarios.
- [$project (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/project.md): Use the ``$project`` aggregation stage to reshape documents for the next pipeline stage by specifying the fields to include, exclude, or compute in the output. Passes documents with fields to next stage in pipeline.
- [$push (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/push.md): Explore how to use the `$push` operator in MongoDB aggregation stages to create arrays from document values.
- [$querySettings (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/querySettings.md)
- [$queryStats (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/queryStats.md): Explore how to use the `$queryStats` aggregation stage to collect runtime statistics for queries, including syntax, requirements, and output details.
- [Toggle $queryStats Log Output](https://www.mongodb.com/docs/manual/reference/operator/aggregation/queryStats/toggle-logging.md): Toggle the logging of `$queryStats` output in MongoDB Atlas to manage performance impact and information detail.
- [$radiansToDegrees (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/radiansToDegrees.md): Convert radians to degrees using the `$radiansToDegrees` aggregation operator, handling `null`, `NaN`, and infinity values.
- [$rand (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/rand.md): Generate random float values between 0 and 1 using the `$rand` operator in MongoDB aggregation pipelines.
- [$range (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/range.md): Explore how to use the `$range` operator in MongoDB to generate sequences of numbers for aggregation operations.
- [$rank (Window Function) (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/rank.md): Explore how to use the `$rank` operator in MongoDB's `$setWindowFields` stage to determine document positions within partitions based on specified fields.
- [$rankFusion (aggregation)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/rankFusion.md): Learn how to use an aggregation stage to combine the results of multiple ranked aggregation pipelines.
- [$redact (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/redact.md): Restrict document content using `$redact` aggregation based on embedded document information and system variables like `$$DESCEND`, `$$PRUNE`, and `$$KEEP`.
- [$reduce (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/reduce.md): Apply the `$reduce` operator to combine array elements into a single value using specified expressions in MongoDB aggregation.
- [$regexFind (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/regexFind.md): Utilize `$regexFind` in MongoDB aggregation to match regex patterns and return details of the first match, including captured groups.
- [$regexFindAll (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/regexFindAll.md): Utilize `$regexFindAll` in aggregation expressions for regex pattern matching, returning an array of match details or an empty array if no match is found.
- [$regexMatch (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/regexMatch.md): Perform regex pattern matching in MongoDB aggregations using `$regexMatch` to return true or false based on match existence.
- [$replaceAll  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/replaceAll.md): Replace all instances of a search string in an input string with a replacement string using the `$replaceAll` operator in MongoDB aggregation.
- [$replaceOne  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/replaceOne.md): Replace the first occurrence of a search string in an input string using the `$replaceOne` aggregation operator. Case-sensitive and diacritic-sensitive.
- [$replaceRoot (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/replaceRoot.md): Replace the input document with a specified document using `$replaceRoot` in MongoDB aggregation, promoting embedded documents or creating new ones as the new root.
- [$replaceWith (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/replaceWith.md): Use the `$replaceWith` aggregation stage to replace documents, promote embedded documents to the top level, or build new documents from an expression.
- [$reverseArray  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/reverseArray.md): Use `$reverseArray` in MongoDB to reverse the order of elements in an array expression, returning null for non-array inputs.
- [$round  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/round.md): Use `$round` to round numbers to specified decimal places or whole integers, supporting even rounding and handling special values like `null` and `NaN`.
- [$rtrim  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/rtrim.md): Use `$rtrim` in MongoDB to remove specified characters or whitespace from the end of a string in aggregation operations.
- [$sample (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sample.md): Use the $sample aggregation stage to randomly select a specified number of documents from a MongoDB collection. Learn about the syntax, behavior, and usage.
- [$sampleRate  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sampleRate.md): Use `$sampleRate` in aggregation to randomly select documents based on a specified probability, expressed as a percentage.
- [$score (aggregation)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/score.md): Use the $score aggregation stage to compute and return a new score as metadata. Learn how to normalize values and view detailed ranking information.
- [$scoreFusion (aggregation)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/scoreFusion.md): Learn how to use an aggregation stage to combine the results of multiple scored aggregation pipelines.
- [$search (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/search.md): Perform full-text searches in Atlas collections using the `$search` aggregation pipeline stage with MongoDB Search indexes.
- [$searchMeta (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/searchMeta.md): Explore how `$searchMeta` returns metadata for MongoDB Search queries using indexed fields in Atlas collections.
- [$second  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/second.md): Use the `$second` operator in MongoDB to extract the second from a date, accommodating leap seconds, with optional timezone support.
- [$serializeEJSON (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/serializeEJSON.md): Converts BSON values to Extended JSON format, preserving type information or using relaxed mode for readability. Use with $toString to generate JSON strings.
- [$set (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/set.md): Use the $set aggregation stage to add new fields to documents or overwrite the values of existing fields in the aggregation pipeline. $set outputs documents that contain all existing fields from the input documents and the new fields.
- [$setDifference  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/setDifference.md): Perform set operations with `$setDifference` to find elements unique to the first array in MongoDB aggregation.
- [$setEquals  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/setEquals.md): Compare arrays using `$setEquals` to check if they contain the same distinct elements, ignoring duplicates and order.
- [$setField  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/setField.md): Modify documents by adding, updating, or removing fields using the `$setField` operator in MongoDB aggregation.
- [$setIntersection  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/setIntersection.md): Use `$setIntersection` to find common elements in arrays, treating them as sets, and return unique entries in the result.
- [$setIsSubset  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/setIsSubset.md): Determine if one array is a subset of another using the `$setIsSubset` operator in MongoDB aggregation.
- [$setUnion (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/setUnion.md): Use `$setUnion` to combine multiple arrays into one, filtering out duplicates and treating arrays as sets.
- [$setWindowFields (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/setWindowFields.md): Use the `$setWindowFields` aggregation stage to run operations on a span of documents and return computed results without modifying the source documents.
- [$shardedDataDistribution (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/shardedDataDistribution.md): Retrieve data distribution metrics for sharded collections using the `$shardedDataDistribution` aggregation stage on `mongos`.
- [$shift  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/shift.md): Use the `$shift` operator in the `$setWindowFields` stage to return a field value from a document at a specified position relative to the current document.
- [$sigmoid  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sigmoid.md)
- [$similarityCosine (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/similarityCosine.md): Use $similarityCosine in MongoDB aggregation to compute the cosine similarity between two numeric vectors. Returns a raw score in [-1, 1] or a normalized score in [0, 1].
- [$similarityDotProduct (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/similarityDotProduct.md): Use $similarityDotProduct in MongoDB aggregation to compute the dot product between two numeric vectors. Returns a raw score or a normalized score in [0, 1].
- [$similarityEuclidean (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/similarityEuclidean.md): Use $similarityEuclidean in MongoDB aggregation to compute the Euclidean distance between two numeric vectors. Returns a raw distance or a normalized score in (0, 1].
- [$sin  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sin.md): Calculate the sine of a value in radians using the `$sin` operator, with examples for handling different input types.
- [$sinh  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sinh.md): Calculate the hyperbolic sine of a value in radians using the `$sinh` operator in MongoDB aggregation.
- [$size  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/size.md): Learn about the $size aggregation operator, which counts and returns the total number of items in an array.
- [$skip (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/skip.md): Use the $skip aggregation stage to skip a specified number of documents in a MongoDB aggregation pipeline and pass the remaining documents to the next stage.
- [$slice  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/slice.md): Use the `$slice` aggregation operator to return a subset of an array, specifying the start position and number of elements.
- [$sort (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sort.md): Use the MongoDB $sort aggregation stage to sort documents in ascending or descending order by one or more fields. The sorted documents are passed to the next pipeline stage.
- [$sortArray  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sortArray.md): Sort arrays in MongoDB using `$sortArray` by specifying the sort order for array elements, including sorting by document fields or values.
- [$sortByCount (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sortByCount.md): Group and count documents by a specified expression using `$sortByCount`. Each output document contains an _id field with the grouping value and a count field.
- [$split  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/split.md): Divide strings into arrays using the `$split` operator in MongoDB aggregation, specifying a delimiter to separate substrings.
- [$sqrt (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sqrt.md): Calculate the square root of a positive number using the `$sqrt` operator in MongoDB aggregation, returning results as a double or decimal.
- [$stdDevPop (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/stdDevPop.md): Calculate the population standard deviation of input values using `$stdDevPop` in various aggregation stages, ignoring non-numeric values.
- [$stdDevSamp (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/stdDevSamp.md): Calculate the sample standard deviation of input values using `$stdDevSamp` in various aggregation stages, ignoring non-numeric values.
- [$strLenBytes (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/strLenBytes.md): Calculate the number of UTF-8 encoded bytes in a string using the `$strLenBytes` operator in MongoDB aggregation.
- [$strLenCP (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/strLenCP.md): Calculate the number of UTF-8 code points in a string using the `$strLenCP` operator in MongoDB aggregation.
- [$strcasecmp (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/strcasecmp.md): Perform case-insensitive string comparisons using the `$strcasecmp` operator in MongoDB aggregation.
- [$substr (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/substr.md): Use `$substr` to extract a substring from a string in MongoDB aggregation, specifying start index and length.
- [$substrBytes (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/substrBytes.md): Use `$substrBytes` to extract a substring from a string based on UTF-8 byte index and count, handling single and multibyte characters.
- [$substrCP  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/substrCP.md): Extract substrings from strings using the `$substrCP` operator based on UTF-8 code points in MongoDB aggregation.
- [$subtract (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/subtract.md): Use `$subtract` in MongoDB to calculate differences between numbers, dates, or a date and milliseconds, with examples demonstrating its syntax and behavior.
- [$subtype (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/subtype.md): Use the `$subtype` operator in MongoDB to return the subtype of a value in aggregation expressions.
- [$sum (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/sum.md): Learn how to use the MongoDB $sum aggregation operator to calculate the sum of numeric values across documents. $sum ignores non-numeric and non-existent fields.
- [$switch (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/switch.md): Evaluate case expressions with `$switch` in MongoDB aggregation, executing the first true case or a default expression if none match.
- [$tan (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/tan.md): Calculate the tangent of a value in radians using the `$tan` operator in MongoDB aggregation.
- [$tanh (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/tanh.md): Calculate the hyperbolic tangent of a value in radians using the `$tanh` operator in MongoDB aggregation.
- [$toArray (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toArray.md): Use the $toArray aggregation expression to convert a value to an array in a MongoDB pipeline. Learn about syntax, input type behavior, and see code examples.
- [$toBool (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toBool.md): Learn how to use the $toBool aggregation expression to convert a value to a boolean, including the input types it accepts and its $convert shorthand syntax.
- [$toDate (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toDate.md): Learn how to use the $toDate aggregation expression to convert a value to a date, including the input types it accepts and its $convert shorthand syntax.
- [$toDecimal (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toDecimal.md): Learn how to use the $toDecimal aggregation expression to convert a value to a decimal, including the input types it accepts and its $convert shorthand syntax.
- [$toDouble (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toDouble.md): Learn how to use the $toDouble aggregation expression to convert a value to a double, including the input types it accepts and its $convert shorthand syntax.
- [$toHashedIndexKey (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toHashedIndexKey.md): Compute hash values in an aggregation pipeline using `$toHashedIndexKey`, which uses the same hash function as MongoDB's hashed index but without collation.
- [$toInt (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toInt.md): Learn how to use the $toInt aggregation expression to convert a value to an integer, including the input types it accepts and its $convert shorthand syntax.
- [$toLong  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toLong.md): Learn how to use the $toLong aggregation expression to convert a value to a long, including the input types it accepts and its $convert shorthand syntax.
- [$toLower  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toLower.md): Convert strings to lowercase using the `$toLower` aggregation operator, which returns an empty string for null values.
- [$toObject (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toObject.md): Learn how to use the $toObject aggregation expression to convert a string to an object, including the input types it accepts and the JSON parsing rules.
- [$toObjectId  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toObjectId.md): Learn how to use the $toObjectId aggregation expression to convert a value to an ObjectId, including the input types it accepts and its $convert shorthand.
- [$toString  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toString.md): Convert values to strings using `$toString` in MongoDB aggregation, with examples of input types and conversion results.
- [$toUUID  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toUUID.md)
- [$toUpper  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/toUpper.md): Convert strings to uppercase using the `$toUpper` aggregation operator, which returns an empty string for null values.
- [$top (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/top.md): Use the `$top` accumulator to return the top element within a group based on specified sort order in MongoDB aggregation.
- [$topN (accumulator operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/topN.md): Use `$topN` to aggregate the top elements within a group based on a specified sort order in MongoDB.
- [$trim  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/trim.md): Use the `$trim` operator in MongoDB to remove whitespace or specified characters from the beginning and end of a string in aggregation operations.
- [$trunc  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/trunc.md): Use `$trunc` in MongoDB to truncate numbers to a whole integer or specified decimal place in aggregation operations.
- [$tsIncrement  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/tsIncrement.md): Use `$tsIncrement` to obtain the incrementing ordinal from a timestamp, uniquely identifying events occurring within the same second.
- [$tsSecond  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/tsSecond.md): Use `$tsSecond` to extract seconds from a timestamp in MongoDB aggregation pipelines, returning a `long` value.
- [$type  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/type.md): Use the `$type` aggregation operator to return the BSON type of an argument, such as string"
- [$unionWith (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/unionWith.md): Use `$unionWith` to combine two aggregations into a single result set, allowing for duplicate entries and supporting various MongoDB aggregation pipeline stages.
- [$unset (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/unset.md): Remove fields from documents using the `$unset` aggregation stage, which can exclude single or multiple fields, including embedded fields.
- [$unsetField  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/unsetField.md): Remove specified fields from documents using the `$unsetField` operator in MongoDB aggregation pipelines.
- [$unwind (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/unwind.md): Use the $unwind aggregation stage to deconstruct an array field and output one document per element. Explore options for preserving missing arrays and tracking array indexes in MongoDB.
- [$vectorSearch (aggregation stage)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/vectorSearch.md): Perform semantic searches on vector embeddings in Atlas clusters using the `$vectorSearch` aggregation stage.
- [$week  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/week.md): Use the `$week` operator in MongoDB to determine the week number of a given date, with options for timezone specification.
- [$year  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/year.md): Extract the year from a date using the `$year` aggregation operator, with optional timezone support.
- [$zip  (expression operator)](https://www.mongodb.com/docs/manual/reference/operator/aggregation/zip.md): Transpose arrays using the `$zip` operator in MongoDB aggregation, with options for handling arrays of different lengths.