underliningvsunderpinningWhich spelling fits?

Quick tell: underlining is a verb, underpinning is a noun, so they fill different roles in a sentence.

Which to use

“underlining” is a verb and “underpinning” is a noun - they look or sound alike but fill different roles in a sentence.

#42,468
“underlining” frequency rank
#33,896
“underpinning” frequency rank
76364
confusion score

Side-by-Side Comparison

Feature underlining underpinning
Definition present participle and gerund of underline A support or foundation, especially as a structure of masonry that supports a wall.

Letter map: underlining vs underpinning

Shared letters muted; letters that set underlining and underpinning apart highlighted. Shared run: 10.

11 ch
underlining
12 ch
underpinning

Grammar separator: underlining vs underpinning

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: underlining is averb and underpinninganoun. On the page they differ by 1 letter(s) in length. Our composite confusion score for this pair is 76364, derived from the frequency rank of both members and their visual similarity.

underlining is recorded at frequency rank #42,468, classified as averb. underpinning is at rank #33,896, tagged as anoun.

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 76364, this pair ranks #30,338 of 530,003 scored English confusable pairs - among the most confusable pairs.

Orthographic DNA of underlining vs underpinning

Shared letters: deginru. Private to "underlining": l. Private to "underpinning": p.

"underlining" · 11 letters · shape VCCVCCVCVCC  ·  "underpinning" · 12 letters · shape VCCVCCVCCVCC

Known mistypes of this pair

  • underliningnuderlining · udnerlining · undderlining · undelrining · underilning · underliinng · underlinign · underliningg
  • underpinningnuderpinning · udnerpinning · undderpinning · undeprinning · underipnning · underpining · underpininng · underpinnign

Frequently Asked Questions

Do "underlining" and "underpinning" mean the same thing in a sentence?
No - they are not even the same part of speech. "underlining" is a verb and "underpinning" a noun, so a sentence built for one is usually ungrammatical with the other.
In ordinary English text, does "underlining" or "underpinning" show up more?
"underpinning" is the more common of the two: it sits at frequency rank #33,896 in our English list, against #42,468 for "underlining". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

After this comparison

Pair "underlining" vs "underpinning" is on the table, pick a follow-up below.

  • Full dictionary entry for "underlining" with definition, IPA, and generated misspellings. Word entry
  • Full dictionary entry for "underpinning" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #30,338 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
  • "underlining" and "underpinning" also get mixed up with nearby pairs, the highest-scored neighbour is "underlining vs undermining". Nearby pair
  • Recorded mistypes exist for at least one side of this pair, useful when a spell-checker or OCR lands on the wrong form. See mistypes

Confusion rank #30,338 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list