Create — create an Observable from scratch by calling observer methods programmatically
Defer — do not create the Observable until the observer subscribes, and create a fresh Observable for each observer
Empty/Never/Throw — create Observables that have very precise and limited behavior
From — convert some other object or data structure into an Observable
Interval — create an Observable that emits a sequence of integers spaced by a particular time interval
Just — convert an object or a set of objects into an Observable that emits that or those objects
Range — create an Observable that emits a range of sequential integers
Repeat — create an Observable that emits a particular item or sequence of items repeatedly
Start — create an Observable that emits the return value of a function
Timer — create an Observable that emits a single item after a given delay

Buffer — periodically gather items from an Observable into bundles and emit these bundles rather than emitting the items one at a time
FlatMap — transform the items emitted by an Observable into Observables, then flatten the emissions from those into a single Observable
GroupBy — divide an Observable into a set of Observables that each emit a different group of items from the original Observable, organized by key
Map — transform the items emitted by an Observable by applying a function to each item
Scan — apply a function to each item emitted by an Observable, sequentially, and emit each successive value
Window — periodically subdivide items from an Observable into Observable windows and emit these windows rather than emitting the items one at a time

Debounce — only emit an item from an Observable if a particular timespan has passed without it emitting another item
Distinct — suppress duplicate items emitted by an Observable
ElementAt — emit only item n emitted by an Observable
Filter — emit only those items from an Observable that pass a predicate test
First — emit only the first item, or the first item that meets a condition, from an Observable
IgnoreElements — do not emit any items from an Observable but mirror its termination notification
Last — emit only the last item emitted by an Observable
Sample — emit the most recent item emitted by an Observable within periodic time intervals
Skip — suppress the first n items emitted by an Observable
SkipLast — suppress the last n items emitted by an Observable
Take — emit only the first n items emitted by an Observable
TakeLast — emit only the last n items emitted by an Observable

And/Then/When — combine sets of items emitted by two or more Observables by means of Pattern and Plan intermediaries
CombineLatest — when an item is emitted by either of two Observables, combine the latest item emitted by each Observable via a specified function and emit items based on the results of this function
Join — combine items emitted by two Observables whenever an item from one Observable is emitted during a time window defined according to an item emitted by the other Observable
Merge — combine multiple Observables into one by merging their emissions
StartWith — emit a specified sequence of items before beginning to emit the items from the source Observable
Switch — convert an Observable that emits Observables into a single Observable that emits the items emitted by the most-recently-emitted of those Observables
Zip — combine the emissions of multiple Observables together via a specified function and emit single items for each combination based on the results of this function

Catch — recover from an onError notification by continuing the sequence without error
Retry — if a source Observable sends an onError notification, resubscribe to it in the hopes that it will complete without error

Delay — shift the emissions from an Observable forward in time by a particular amount
Do — register an action to take upon a variety of Observable lifecycle events
Materialize/Dematerialize — represent both the items emitted and the notifications sent as emitted items, or reverse this process
ObserveOn — specify the scheduler on which an observer will observe this Observable
Serialize — force an Observable to make serialized calls and to be well-behaved
Subscribe — operate upon the emissions and notifications from an Observable
SubscribeOn — specify the scheduler an Observable should use when it is subscribed to
TimeInterval — convert an Observable that emits items into one that emits indications of the amount of time elapsed between those emissions
Timeout — mirror the source Observable, but issue an error notification if a particular period of time elapses without any emitted items
Timestamp — attach a timestamp to each item emitted by an Observable
Using — create a disposable resource that has the same lifespan as the Observable

All — determine whether all items emitted by an Observable meet some criteria
Amb — given two or more source Observables, emit all of the items from only the first of these Observables to emit an item
Contains — determine whether an Observable emits a particular item or not
DefaultIfEmpty — emit items from the source Observable, or a default item if the source Observable emits nothing
SequenceEqual — determine whether two Observables emit the same sequence of items
SkipUntil — discard items emitted by an Observable until a second Observable emits an item
SkipWhile — discard items emitted by an Observable until a specified condition becomes false
TakeUntil — discard items emitted by an Observable after a second Observable emits an item or terminates
TakeWhile — discard items emitted by an Observable after a specified condition becomes false

Average — calculates the average of numbers emitted by an Observable and emits this average
Concat — emit the emissions from two or more Observables without interleaving them
Count — count the number of items emitted by the source Observable and emit only this value
Max — determine, and emit, the maximum-valued item emitted by an Observable
Min — determine, and emit, the minimum-valued item emitted by an Observable
Reduce — apply a function to each item emitted by an Observable, sequentially, and emit the final value
Sum — calculate the sum of numbers emitted by an Observable and emit this sum

backpressure operators — strategies for coping with Observables that produce items more rapidly than their observers consume them

Connect — instruct a connectable Observable to begin emitting items to its subscribers
Publish — convert an ordinary Observable into a connectable Observable
RefCount — make a Connectable Observable behave like an ordinary Observable
Replay — ensure that all observers see the same sequence of emitted items, even if they subscribe after the Observable has begun emitting items

To — convert an Observable into another object or data structure