Glossary

Common terms used throughout this guide.

A

AGP (Android Gradle Plugin)

The Gradle plugin that builds Android apps; its version must be compatible with the Gradle and Kotlin versions.

Activity

An Android component representing a single screen with a UI.

C

Composable

A @Composable function that describes UI in Jetpack Compose.

Coroutine

A lightweight, suspendable computation for asynchronous code without blocking threads.

Companion object

An object declared inside a class for members tied to the class itself (like static in Java).

D

Data class

A class whose equals/hashCode/toString/copy are generated from its properties.

Dispatcher

Decides which thread(s) a coroutine runs on (Default, IO, Main).

DSL

Domain-specific language; in Kotlin, built with lambdas-with-receiver.

E

Extension function

A function added to a type from outside its definition.

F

Flow

A cold asynchronous stream of values, like a suspending sequence.

N

Null safety

Kotlin’s type-system feature distinguishing nullable (T?) from non-null (T) types.

S

Sealed class/interface

A type with a fixed, compiler-known set of subtypes, enabling exhaustive when.

StateFlow

A hot flow that always holds the latest value; the standard way to expose UI state.

Suspend function

A function that can pause and resume without blocking its thread.

V

Variance

How subtyping of a generic relates to its type argument (out = covariant, in = contravariant).

ViewModel

A lifecycle-aware holder of UI state that survives configuration changes.

W

WorkManager

An Android library for deferrable, guaranteed background work.