fill in

verb

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

"fill-in" is a 6-letter English headword indexed on PlainSpell.

The verdict

“fill in” is outside the top-ranked English vocabulary, used as a verb - the kind of word writers most often double-check.

Unranked
below top-frequency English
7
letters

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - To fill; to replace material that is absent or has been removed.

Key facts for fill in
PropertyValue
Headwordfill in
LanguageEnglish
Part of speechVerb
Letters7
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Where “fill in” sits in English frequency

fill in falls outside the top-100,000 ranked English words, the long-tail zone of technical, archaic, or low-frequency vocabulary, exactly where readers second-guess spellings most.

Beyond rank #100,000. Source: FrequencyWords open word-frequency list.

Spelling & Dictionary Insight

The English entry for fill in is 7 letters long, classified as a verb. It sits outside the most-frequent rank tiers, which is often why uncommon words generate more spelling variants per reader. Wiktionary records 5 distinct senses for this headword, so context determines which meaning a reader should apply.

We couldn't generate a plausible misspelling set for fill in, which points to an orthography that plays by predictable English rules. Our confusable-pair dataset has no match for it, since nothing in our dataset looks or sounds close enough to cause mix-ups.

No borrowing history is documented for this entry, so its spelling is easiest explained by how it's pronounced rather than where it came from. The correct English form is fill in, spelled F-I-L-L- -I-N.

Definition

  1. 1
    To fill; to replace material that is absent or has been removed.
  2. 2
    To inform somebody, especially to supply someone missing or missed information.
  3. 3
    To substitute for somebody or something.
  4. 4
    To complete a form or questionnaire with requested information.
  5. 5
    To beat up; to physically assault.

This word in other languages

informar(Español)renseigner(Français)ersetzen(Deutsch)substituir(Português)

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "fill in"?
"fill in" is spelled F-I-L-L- -I-N.
What does "fill in" mean?
As a verb, "fill in" means: To fill; to replace material that is absent or has been removed.
What language does "fill in" come from?
"fill in" is a English word. You can look up definitions, pronunciations, and spelling data for this and other words across English, Spanish, Portuguese, French, and German on PlainSpell.
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.

Using “fill in”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is F-I-L-L- -I-N - every other letter order is a misspelling in standard orthography.
  • Browse more English words and confusable pairs in the same reference. English words
Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

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

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list