Say it like this
- This function has too many side effects
- We need to eliminate side effects from this module
- Be careful about side effects when refactoring
Use it at work
Code review
- This function has a side effect: it writes to the database.
- Let's move the side effect out of the getter.
Debugging
- The bug comes from a side effect in the constructor.
- Unexpected side effects make tests flaky.
General
- A side effect of the change is slower startup.
- One good side effect: fewer support tickets.
Don't say this
Side effect means an unintended state change, not a result or benefit. Use 'benefit' or 'result' for positive outcomes.
Don't mix it up
| Term | What it is | Who writes or uses it | When |
|---|---|---|---|
| side effect | Change outside the function | Developers | I/O, state |
| pure function | Function with no side effects | Developers | Logic |
Practice
Try it
4 quick exercises
1. Your teammate wrote a function that modifies global variables. You want to flag this in code review. Which sounds most natural?
2. We should refactor the API handler to _______ _______ because it makes testing difficult.
3. Which sentence uses side effect incorrectly?
4. Rewrite this in natural tech English using side effect: The problem with this code is that it changes things it should not change, and that makes it difficult to understand what it does.
Say it out loud
Phrase 1 of 3
"This function has too many side effects"
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More about side effect
Real examples(3)
- in a code review
"This function modifies the global cache as a side effect, which makes it harder to unit test."
- in a standup
"We discovered that the authentication function had an unexpected side effect of clearing user sessions."
- in a team meeting
"To improve maintainability, we should refactor these components to minimize side effects."
More mistakes(2)
Handle with care. Non-tech speakers may confuse it with the medical meaning (adverse reaction to medicine). In tech, it refers to when code changes something beyond its intended output, not about negative consequences.
- ✕This function is side effect.✓This function has side effects or This is a pure function without side effects.
Side effect is a noun phrase, not an adjective. You cannot describe something as side effect; you describe what has side effects.
- ✕Can you side effect this code?✓Can you remove the side effects from this code?
Side effect is not typically used as a verb. Use phrases like remove side effects, minimize side effects, or manage side effects.
Other forms(3)
- side effect noun
"The function has a side effect that modifies the database."
- side effects (plural) noun phrase
"We need to eliminate the side effects in this module."
- side-effect-free or pure adjective
"Pure functions are side-effect-free and easier to test."
Often used with(5)
- has side effects · Most common collocation; describes when code causes unintended state changes
- minimize side effects · Describes the goal of reducing unwanted state changes in code
- unintended side effect · Emphasizes that the state change was not planned or expected
- side effects occur · Describes when side effects happen during execution
- remove side effects · Describes refactoring code to eliminate state changes
Similar words(3)
- unintended consequence · More general term; side effect is more specific to code behavior
- state mutation · More technical; refers specifically to changing program state
- external change · Broader term; side effect is more precise in technical contexts
Opposites(2)
- pure function
- no side effects
Questions(5)
- What does side effect mean in software engineering?
- In software engineering, a side effect is any change in program state that occurs as a result of executing code, beyond the functions primary return value. This includes modifying global variables, changing files on disk, updating a database, writing to the console, or altering class state. Side effects make code less predictable and harder to test, which is why developers try to minimize them.
- How do you use side effect in a sentence at work?
- You typically use it when describing code behavior in reviews or meetings. Examples: 'This function has side effects that make it difficult to test,' 'We need to refactor this module to remove side effects,' or 'The caching mechanism has an unintended side effect of storing stale data.' You can also use it in phrases like side-effect-free or side effects occur.
- Is side effect formal or informal?
- Side effect is neutral in formality. It is equally appropriate in casual standups, formal code reviews, architecture documents, and job interviews. It is standard technical terminology used by all levels of engineers.
- What is the difference between side effects and errors?
- Side effects are not errors. They are unintended state changes that may or may not cause problems. An error is when code fails to execute or produces an exception. However, side effects can make errors harder to diagnose because they change system state in unexpected ways.
- Why do developers want to eliminate side effects?
- Developers minimize side effects because they make code harder to test, debug, reason about, and maintain. Functions without side effects (pure functions) always produce the same output for the same input, making them predictable and reliable. This is especially important in large systems where unexpected state changes can cause subtle bugs.
