# English a vs an rule

> Why 'an' and 'a' confuse spellers
- Title: English a vs an rule · Redblobgames | Shortify
- Summary: Why 'an' and 'a' confuse spellers Spoken vowel sounds, not written letters, determine English articles english, article, vowel · reported by Redblobgames.
- Keywords: english, article, vowel, spelling, cmudict, ipa, technology, startups, rule, Redblobgames
- Source: Redblobgames — https://redblobgames.com/blog/2026-09-16-english-a-vs-an
- Read time: 1 min
- Topics: english, article, vowel, spelling, cmudict, ipa, technology, startups
## Spoken sounds matter
The rule for 'a' and 'an' depends on spoken vowel sounds, not written letters.
## Unicorn example
Unicorn starts with a vowel letter but a consonant sound, so it takes 'a'.
## Hour example
Hour starts with a consonant letter but a vowel sound, so it takes 'an'.
## Rare exceptions
Only 129 out of 32,455 words need special rules for articles.
## Why this matters
Procedural text generation must account for spoken sounds, not spelling.
## Key takeaway

Spoken vowel sounds, not written letters, determine English articles