# Rule 2.3 — Use Hyphens Between Words Used as One Unit

> **Source:** Adapted from ASD-STE100 Issue 9, Rule 2.3

> **Source:** [master.md#sec2-rule2.3](ste-code/grouped/)

> Source: master.md#sec2-rule2.3

## Original Rule

#### Method 2 - Hyphens (-) between the words that you use as one unit

A hyphen is a punctuation mark that connects words or parts of words. You can use hyphens between words to show how related words operate as one unit. This method will make the multi-word nouns that you use agree with rule 2.1. Hyphenated words always count as one word.

##### Examples in STE

| Example | Note |
|---|---|
| Make sure that the cutoff-switch power connection is safe. | (3 words) |
| Inspection of the lavatory rapid-decompression device. | (3 words) |

Make sure that you do not connect words which are not related, because this hyphen will change the meaning of the multi-word noun. If you are not sure, only explain the multi-word noun. Then, use a shorter form, or an official approved abbreviation.

If an approved technical noun includes hyphens, do not change it. If it is too long, write it in full the first time it occurs and then use the recommended method (shorter technical nouns) specified in this rule.

Do not use hyphens to make groups of more than three words. If you use hyphens for all the words, this multi-word noun will not be easy to read and understand.

##### Example

> **Non-STE:** Move the main-gear-door-retraction-winch handle. (2 words, but not correct)
>
> **STE:** Move the main-gear-door retraction-winch handle. (3 words)

If an approved technical noun includes three words or less (for example "poppet valve assembly" and "diaphragm assembly"), it is not necessary to use hyphens.

##### Example

| Do not write: | WRITE: |
|---|---|
| A. Remove the diaphragm-assembly (8) from the valve body (20). B. Remove the poppet-valve assembly (15) from its seat. | A. Remove the diaphragm assembly (8) from the valve body (20). B. Remove the poppet valve assembly (15) from its seat. |

But, if an approved technical noun includes a hyphen (for example "inward-outward valve"), do not remove the hyphen. Keep the technical noun that comes from your official company documentation.

##### Example

> **Non-STE:** <u><mark>Do not write: The inward outward valve is part of the fuel system.</mark></u>
>
> **STE:** <mark>WRITE: The inward-outward valve is part of the fuel system.</mark>

## Adapted Rule

A hyphen is a punctuation mark that connects words or parts of words. Use hyphens between words to show how related words operate as one unit. This method will make the multi-word code nouns that you use agree with rule 2.1. Hyphenated words always count as one word.

Do not connect words that are not related, because the hyphen will change the meaning of the multi-word code noun. If you are not sure, only explain the multi-word code noun. Then, use a shorter form, or an official approved abbreviation.

If an approved technical code noun includes hyphens, do not change it. If it is too long, write it in full the first time it occurs and then use the recommended method (shorter technical nouns) specified in this rule.

Do not use hyphens to make groups of more than three words. If you use hyphens for all the words, this multi-word code noun will not be easy to read and understand.

### Examples in STE-Code

| Example | Note |
|---|---|
| Make sure that the fail-safe shutdown handler connection is safe. | (3 words) |
| Inspection of the request rate-limit device. | (3 words) |

> **Non-STE:** Move the main-feature-flag-rollback-handler trigger. (2 words, but not correct)
>
> **STE:** Move the main-feature-flag rollback-handler trigger. (3 words)

If an approved technical code noun includes three words or less (for example "pipeline validator assembly" and "data adapter assembly"), it is not necessary to use hyphens.

| Do not write: | WRITE: |
|---|---|
| A. Remove the data-adapter assembly (8) from the view body (20). B. Remove the pipeline-validator assembly (15) from its seat. | A. Remove the data adapter assembly (8) from the view body (20). B. Remove the pipeline validator assembly (15) from its seat. |

But, if an approved technical code noun includes a hyphen (for example "input-output stream"), do not remove the hyphen. Keep the technical code noun that comes from your official code documentation.

> **Non-STE:** Do not write: The input output stream is part of the logging system.
>
> **STE:** WRITE: The input-output stream is part of the logging system.
