Which to use
“underline” is a noun and “underlying” is an adjective - they look or sound alike but fill different roles in a sentence.
- #29,874
- “underline” frequency rank
- #5,464
- “underlying” frequency rank
- 35338
- confusion score
Side-by-Side Comparison
| Feature | underline | underlying |
|---|---|---|
| Definition | A line placed underneath a piece of text in order to provide emphasis or to indicate that it should be viewed in italics or (in electronic documents) that it acts as a hyperlink. | lying underneath |
Where the spellings diverge
Shared letters are muted; the letters that actually set underline and underlying apart are highlighted. They share 8 letters in sequence, which is exactly why the eye skips the difference.
Spelling & Dictionary Insight
underline and underlying 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 1 letter(s) in length - close enough that the eye skips over the difference, far enough that meaning fully diverges. Our composite confusion score for this pair is 35338, derived from the frequency rank of both members and their visual similarity.
underline is recorded at frequency rank #29,874, classified as anoun, pronounced /ˈʌndɚˌlaɪn/. underlying is at rank #5,464, tagged as anadj.
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 35338, this pair ranks #312,820 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.
Frequency comparison
Frequently Asked Questions
Can "underline" and "underlying" be used interchangeably?
Remembering underline vs underlying
The fastest way to pick the right one every time.
- Check the role first: if you need a noun, it's “underline”; for an adjective, it's “underlying”.
- See each word in full, definition, IPA, etymology and its other confusables. Full “underline” entry
- Browse more pairs most likely to be confused. Most confusable