underline

/ˈʌndɚˌlaɪn/

//ˈʌndɚˌlaɪn// noun

By · According to Wiktionary data (CC BY-SA) ·

"underline" is a 9-letter English headword indexed on PlainSpell.

The verdict

“underline” has 13 generated spelling variants in the English index at frequency #29,874. The variants make it a useful spelling check.

#29,874
frequency rank, English
1,433
“U” headwords
13
tracked misspellings
7
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - 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.

Corpus desk

Index EN-underline · underline · English

underline · rank #29,874 · 13 variants · 7 confusables

  • FREQ-MID #29,874
  • LEN-LONG 9 letters
  • VOW-4 4 vowels
  • CONFUS-MID 7 pairs
  • VAR-HIGH 13 variants
  • BOOK-MID 1,433
  • PHOTO-FINISH uncontrollably

Nearest frequency peer: uncontrollably (-1 rank slots)

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Rank peers near misspelling magnet “underline”

Same rarity band: useful when a typo lands on a peer headword

corpus weight

What this shows “underline” sits among these FrequencyWords peers; misspelling depth is tracked separately in the edit-distance chart.

Source FrequencyWords open word-frequency list As of September 3, 2026

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

underline vs underpin
78% similar
underline vs undermine
89% similar
underline vs underside
78% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for underline
PropertyValue
Headwordunderline
LanguageEnglish
Part of speechNoun
IPA/ˈʌndɚˌlaɪn/
Letters9
Frequency rank#29,874
Misspellings tracked13
Confusable pairs7
SourceWiktionary (kaikki.org)

Frequency seat of misspelling magnet “underline”

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right).underlinelands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Ticks step logarithmically, so each one marks a roughly tenfold drop in how often the word turns up. Same rarity band neighbours include “uncontrollably” (#29,873), “unduly” (#29,875), “unaccompanied” (#29,872). Among 1,433 “U” headwords, “underline” is #29,874. Source: FrequencyWords open word-frequency list.

A misspelling magnet

The generator records 13 spelling variants around underline (IPA /ˈʌndɚˌlaɪn/), anoun. Corpus frequency is #29,874 among 1,433 “U” headwords. Wiktionary lists 4 senses, so context still picks the gloss.

Our generated misspelling index lists 13 likely wrong-spelling variants for underline, with forms such as "nuderline", "udnerline", and "undderline". Every one of these variants traces to a single-character edit -- an added or dropped letter, a swapped consonant, or a vowel swap -- the kind of slip a spell-checker is built to catch. It also participates in 7 confusable-pair relationships, "underpin", "undermine", "underside", and more, where similar look or sound leads writers to substitute one word for another in context.

Etymologically, the entry records: From under- + line. The correct English form is underline, spelled U-N-D-E-R-L-I-N-E.

Definition

  1. 1
    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.
  2. 2
    The character _.
  3. 3
    An announcement of a theatrical performance to follow, placed in an advertisement for the current one.
  4. 4
    A caption beneath a photograph (which may have more than one line of text).

Recorded use

Wiktionary example

These source excerpts show how underline appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. Several readers [...] write to point out that the ex-Great Eastern 0-6-0s now classified as "J20" in the L.N.E.R. lists, no longer hold the supremacy for power among British 0-6-0 locomotives as suggested in the underline to the photograph of one of them which appeared on p. 100 of the March-April issue.

Etymology

From under- + line.

This word in other languages

soulignement(Français)Unterstreichung(Deutsch)underline(Português)

Common misspellings

Also misspelled as:

  • nuderline
  • udnerline
  • undderline
  • undelrine
  • underilne
  • underlien
  • underlinne
  • underlline
  • underlnie
  • underrline
  • undreline
  • unedrline
  • unnderline

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of underline - counted as single-character edits (an insertion, a deletion, or a substituted letter). The larger the bar, the easier the typo is to spot; one-edit slips are the ones that sneak past readers.

nuderline2udnerline2undderline1undelrine2underilne2underlien2underlinne1underlline1
Edit distance from "underline"

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "underline"?
"underline" is spelled U-N-D-E-R-L-I-N-E. The IPA pronunciation is /ˈʌndɚˌlaɪn/.
What does "underline" mean?
As a noun, "underline" means: 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.
What words are commonly confused with "underline"?
"underline" is commonly confused with "underpin", "undermine", "underside". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "underline"?
The IPA (International Phonetic Alphabet) transcription for "underline" is /ˈʌndɚˌlaɪn/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "underline"?
From under- + line. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "underline", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 9 letters (nearest by frequency rank).

weighting#29,889supposing#29,854abhorrent#29,898stillness#29,846

Similar misspelling depth

Headwords with a similar count of attested misspellings (13 here; floor ≥5).

stupidly13 variantsavoidable13 variantsBradbury13 variantsquadratic13 variants

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

Source: FrequencyWords open word-frequency list