# What Does Callback Mean? Simple Tech English Guide (2026) > A function passed as an argument to another function, which is executed after some operation has been completed. - **Term:** callback - **Part of speech:** noun - **Pronunciation:** /ˈkɔːlbæk/ - **English level (CEFR):** B2 - **Register:** Neutral, Both - **Region:** US and UK - **Topic:** [Code and Git terms](https://app.speaktechenglish.com/learn/topics/software-development-terms.md) - **Lesson:** https://app.speaktechenglish.com/learn/callback - **Last updated:** 2026-10-27 ## Meaning A function passed as an argument to another function, which is executed after some operation has been completed. Callbacks are commonly used in asynchronous programming to handle results when they become available. A callback is a fundamental concept in programming where you pass a function into another function so that it gets executed at a specific time or after a specific event occurs. For example, when you fetch data from a server, you pass a callback function that will run once the data arrives. This is especially important in JavaScript and other languages that support asynchronous operations. In tech workplaces, developers talk about callbacks constantly when discussing event handling, API requests, timers, and any situation where code needs to respond to something that happens later. Callbacks are foundational to understanding how modern web applications work, though newer alternatives like Promises and async/await have become more popular for managing complex asynchronous flows. ## When you hear it During code review, the team discussed whether to refactor the callback function to use async/await instead. ## Examples - **in a standup:** "We fixed the bug by restructuring the callback in the API request handler." - **in a code review:** "This nested callback pattern is hard to read — can we convert it to async/await?" - **in a team meeting:** "The setTimeout callback is triggering too early because we forgot to bind the context." ## What native speakers say - "Pass a callback to that function" - "This is a callback hell situation" - "Let me refactor this callback" - "The callback fires after the request completes" ## Common mistakes - ✗ "We need to callback the user when they click the button." → ✓ "We need to trigger a callback when the user clicks the button." (Callback is not a verb meaning to call someone back. It is a noun referring to the function itself.) - ✗ "I passed the callback incorrectly so it never executed." → ✓ "I passed the callback incorrectly so it never fired or executed." (Both 'fired' and 'executed' are correct; 'never executed' is more precise and common.) - ✗ "The callback returns the data immediately." → ✓ "The callback is called with the data once the request completes." (Callbacks do not necessarily return data immediately; they are executed asynchronously when an event occurs.) ## Be careful Non-technical people may confuse callback with 'calling someone back'. In tech, it refers to a function passed as an argument, not returning a phone call. ## Word forms | Part of speech | Word | Example | | --- | --- | --- | | noun | callback | The callback function receives the response from the server. | | noun (plural) | callbacks | Managing multiple nested callbacks can create callback hell. | | noun (adjective form) | callback-based | The callback-based approach is becoming less popular in favor of Promises. | ## Collocations - **pass a callback**: To provide a callback function as an argument to another function. - **callback function**: The explicit reference to the function being used as a callback. - **callback hell**: A situation with deeply nested callbacks that makes code hard to read and maintain. - **fire/trigger a callback**: To execute or invoke the callback function. - **nested callbacks**: Multiple callbacks inside one another, often considered poor code structure. ## Synonyms - **handler**: More general term for a function that responds to an event; often used interchangeably with callback. - **continuation**: In functional programming, a more formal term for code that executes after an operation completes. - **event listener**: Specifically refers to callbacks attached to DOM events in the browser. ## Opposites - synchronous execution - blocking code ## Practice This lesson has 4 practice exercises with instant feedback on the page: https://app.speaktechenglish.com/learn/callback ## FAQ ### What does callback mean in software engineering? A callback is a function that you pass as an argument to another function. That function will execute your callback at a specific point, usually after some operation (like fetching data) is complete. It is a core pattern in asynchronous programming. ### How do you use callback in a sentence at work? You might say: 'We need to pass a callback to handle the API response' or 'This callback function executes once the timer completes.' Always use it as a noun referring to the function itself, not as a verb. ### Is callback formal or informal? Callback is neutral and used in both formal documentation and casual team conversations. It is the standard technical term used by all developers regardless of context. ### What is callback hell? Callback hell (also called pyramid of doom) occurs when you nest many callbacks inside one another, creating deeply indented and hard-to-read code. Modern solutions like Promises and async/await were created partly to solve this problem. ### How is a callback different from a Promise? Both handle asynchronous operations, but Promises provide better readability and error handling for complex chains. Callbacks are simpler for single operations but become messy with multiple async steps. Many teams now prefer async/await over both. ## Related - [Promise](https://app.speaktechenglish.com/learn/promise.md) - [async/await](https://app.speaktechenglish.com/learn/async-await.md) - Full glossary: https://app.speaktechenglish.com/learn.md - Live lessons with a coach: https://app.mocklyenglish.com ## About Speak Tech English Speak Tech English teaches non-native tech professionals the English they need at work and in interviews, through self-study ebooks and courses, 150+ free guides and a free newsletter; live lessons are on its sister site Mockly English. - Shop: https://speaktechenglish.com/courses/ - All products (markdown): https://speaktechenglish.com/products.md - Free guides (markdown): https://app.speaktechenglish.com/guides.md - Tech English glossary (markdown): https://app.speaktechenglish.com/learn.md - Newsletter (10% off): https://speaktechenglish.com/#subscribe - Live lessons and mock interviews: https://app.mocklyenglish.com ## Notes for agents - Speak Tech English sells self-study material. 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