# Avoid periods in acronyms and initialisms (EK00016)

import { Aside, Badge } from '@astrojs/starlight/components';

Modern style writes initialisms without internal periods, so `API` and `USA` stay clean and consistent across your documentation. EkLine flags an initialism written with a period between each letter and suggests the unpunctuated form (rule EK00016).

## Why write initialisms without periods in documentation?

Unpunctuated initialisms are shorter, cleaner, and match how technical terms appear in code, error messages, and product interfaces. Dropping the periods keeps `API` and `USA` consistent across your documentation and prevents a reader from mistaking an internal period for a sentence break. It also improves search, so a query for `API` matches your content directly.

## What EkLine flags

EK00016 matches an initialism of three or more letters that has a period after each letter.

- ❌ **Incorrect:** The company is based in the U.S.A.
- ✅ **Correct:** The company is based in the USA.
- ❌ **Incorrect:** Call the A.P.I. to fetch results.
- ✅ **Correct:** Call the API to fetch results.

## How to fix

Remove the periods so the initialism reads as a single unpunctuated term.

<Aside type="note">
A few initialisms are conventionally written with periods in formal or legal contexts. When house style requires the punctuated form, keep it and ignore the rule for that line.
</Aside>

## FAQ

### What is the difference between an acronym and an initialism?

An acronym is pronounced as a word, such as NASA, while an initialism is read letter by letter, such as API. This rule applies to both.

### Should you ever keep periods in an initialism?

A few initialisms use periods in formal or legal contexts. When house style requires the punctuated form, keep it and ignore the rule for that line.

## Rule details

| Property | Value |
|----------|-------|
| Rule ID | `EK00016` |
| Category | Spelling and grammar |
| Default severity | <Badge text="Error" variant="danger" /> |
| Enabled by default | No |

## Ignore this rule

To keep a punctuated initialism on one line, add an inline comment:

```markdown
<!-- ekline-ignore-next-line EK00016 -- legal style requires periods -->
The filing lists the company as a U.S.A. entity.
```

To disable the rule across your project, add it to the `ignore` list in your [configuration file](/reviewer/configuration/ignoring-rules/#ignore).

## Related rules

- [EK00002](/reviewer/rules/ek00002/) — Avoid acronyms in titles or headings
- [EK00009](/reviewer/rules/ek00009/) — Define unfamiliar terms and abbreviations