Kotlin Coroutines simplify asynchronous programming by providing structured concurrency. Coroutines are lightweight threads that can be suspended without blocking the main thread. launch starts a coroutine that returns a Job; async returns Deferred for result. suspend functions mark code that can be paused and resumed. Dispatchers determine which thread pool runs the coroutine: Main for UI, IO for network/disk, Default for CPU work. CoroutineScope manages coroutine lifecycle tied to Android components. viewModelScope automatically cancels coroutines when ViewModel is cleared. withContext switches dispatchers without nesting coroutines. Error handling uses try-catch within coroutines or CoroutineExceptionHandler. structured concurrency ensures parent coroutines wait for children. flow provides cold asynchronous data streams. StateFlow and SharedFlow provide hot data streams for UI state. combine merges multiple flows, to new flow. Room, Retrofit, and WorkManager now support coroutines natively. Testing coroutines uses runBlockingTest and TestCoroutineDispatcher. Use supervisorScope for isolated child failures. Coroutines eliminate callback hell and reduce boilerplate compared to RxJava. They are the recommended approach for async operations in Android.
