What is the purpose and application of the suspend keyword in programming languages?

The keyword suspend in Kotlin (often used in Android development) denotes a function that can be paused and resumed later without blocking the thread.

This is the basis of coroutines — a mechanism for asynchronous and non-blocking programming. Functions with suspend can only be called from other suspend functions or coroutines.

Example:

suspend fun fetchData(): String {
    delay(1000) // pauses the coroutine for 1 second
    return "Data loaded"
}

Here, delay is also a suspend function that does not block the thread but simply pauses the execution of the coroutine.