Which to use
“eighteen” is a num and “eighteenth” is an adjective - they look or sound alike but fill different roles in a sentence.
- #9,463
- “eighteen” frequency rank
- #15,392
- “eighteenth” frequency rank
- 24855
- confusion score
Side-by-Side Comparison
| Feature | eighteen | eighteenth |
|---|---|---|
| Definition | The cardinal number occurring after seventeen and before nineteen, represented in Roman numerals as XVIII and in Arabic numerals as 18. | The ordinal form of the number eighteen. |
Where the spellings diverge
Shared letters are muted; the letters that actually set eighteen and eighteenth apart are highlighted. They share 8 letters in sequence, which is exactly why the eye skips the difference.
Spelling & Dictionary Insight
eighteen and eighteenth form a confusable pair in the English index, two distinct headwords that are easily confused because they look alike, sound alike, or both. They differ by 2 extra letter(s) - “eighteen” sits inside “eighteenth” - close enough that the eye skips over the difference, far enough that meaning fully diverges. Our composite confusion score for this pair is 24855, derived from the frequency rank of both members and their visual similarity.
eighteen is recorded at frequency rank #9,463, classified as anum, pronounced /ˈeɪ(t).tin/. eighteenth is at rank #15,392, tagged as anadj, pronounced /ˌeɪˈtiːnθ/.
Glosses for this pair are partially populated in our dataset, but the full side-by-side definitions above should still guide you to the right choice.
With a confusion score of 24855, this pair ranks #398,817 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.
Frequency comparison
Frequently Asked Questions
Can "eighteen" and "eighteenth" be used interchangeably?
Remembering eighteen vs eighteenth
The fastest way to pick the right one every time.
- Check the role first: if you need a num, it's “eighteen”; for an adjective, it's “eighteenth”.
- See each word in full, definition, IPA, etymology and its other confusables. Full “eighteen” entry
- Browse more pairs most likely to be confused. Most confusable