Functions Glossary

Browse 20 functions terms defined in plain English, from the cultural dictionary of computing.

20 Functions Terms

Arity
The number of arguments or operands that a function, operator, or constructor accepts. A unary function has arity 1, a binary function arity 2, and so on.
Async Function
A function that can suspend while waiting for asynchronous operations and resume later, usually returning a promise, future, or similar awaitable result. Async...
Callback
A function passed to another function or system to be invoked later in response to an event, completion, or decision point. Callbacks are a foundational...
Callback Function
A function intended to be called by another piece of code after a task completes or an event occurs, often with data about the outcome. The phrase emphasizes...
Calling Convention
The low-level contract that defines how function calls pass arguments, return values, and preserve registers at the machine-code level. Calling conventions are...
Composable Function
A function designed so its output or behavior can be cleanly combined with other functions to build larger behaviors without tight coupling. Composable...
Lambda
An anonymous, inline function defined without a name, originating from lambda calculus. Also refers to AWS Lambda, a serverless compute service.
Lambda Function
In cloud computing, a serverless compute unit (named after AWS Lambda) that runs code in response to events — such as HTTP requests, queue messages, or file...
Method
A function defined on a class or type that operates on an instance's data, receiving the instance as an implicit or explicit first argument (e.g., `self` in...
Parameter
A named variable in a function or method declaration that acts as a placeholder for data passed in at call time. Parameters define what a function expects;...
Parameter Passing
The mechanism by which arguments are transferred from a caller to a function. Common strategies include pass-by-value (the function receives a copy),...
Partial Application
Fixing some arguments of a function to produce a new function with fewer parameters. Unlike currying (which transforms f(a,b,c) into f(a)(b)(c)), partial...
Pass by Reference
A parameter-passing convention in which a function receives a reference (pointer or alias) to the caller's original variable, so modifications inside the...
Pass by Value
A parameter-passing convention in which a function receives an independent copy of the caller's argument, so modifications inside the function have no effect...
Python Decorator
A higher-order function, applied with the @decorator syntax above a function or class definition, that takes the decorated callable as input and returns a...
Return Type
The type annotation on a function or method that declares what kind of value it will produce when it finishes executing. In statically typed languages the...
Return Value
The data that a function or method sends back to its caller upon completion, determined by a return statement or the language's implicit return rules. The type...
Subroutine
A named, reusable block of instructions that performs a specific task, callable from multiple points in a program, known variously as a function, procedure, or...
Variadic Function
A function that accepts a variable number of arguments, such as C's printf(), JavaScript's rest parameters (...args), or Python's *args. The mechanism varies...
Void
A type (or pseudo-type) indicating the absence of a value. As a function return type, void means the function performs a side effect and returns nothing. In C,...

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