add-on

noun

"add-on" is a 5-letter English headword indexed on PlainSpell.

The verdict

“add-on” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.

Unranked
below top-frequency English
6
letters

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - Something which can be appended to something else.

Corpus desk

Index EN-add-on · add-on · English

add-on · unranked · 0 variants · 0 confusables

  • FREQ-UNRANKED Unranked
  • LEN-LONG 6 letters
  • VOW-2 2 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-THIN "A" thin
  • PHOTO-UNK Peer pending

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.

Key facts for add-on
PropertyValue
Headwordadd-on
LanguageEnglish
Part of speechNoun
Letters6
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “add-on” in English

add-onsits beyond the 100,000 most-frequent English words, in the long tail of technical, archaic, or otherwise rare vocabulary where spelling doubt tends to strike hardest.

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

Rare enough to double-check

add-on is uncommon English outside the top frequency list, classed as anoun. Rarity is why readers land here mid-draft. 4 senses are on record.

We couldn't generate a plausible misspelling set for add-on, and the word's spelling is regular enough that our generator found nothing worth flagging. This entry stands alone in our confusable dataset, since no other headword is close enough in sound or shape to pair with it.

Etymologically, the entry records: Deverbal from add on. The correct English form is add-on, spelled A-D-D---O-N.

Definition

  1. 1
    Something which can be appended to something else.
  2. 2
    A software extension or hardware peripheral that provides additional functions or customization for a core application or system.
  3. 3
    Additional chips that can be purchased at specific times in tournament play.
  4. 4
    Synonym of expansion pack.

Recorded use

Wiktionary examples

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

  1. Payments made before an add-on sale must be allocated entirely to the previous contract or contracts.
  2. Microdrives that can hold several gigabytes (see Figure 2.20) have been available as add-ons for portable devices.

Etymology

Deverbal from add on.

Synonyms

This word in other languages

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 "add-on"?
"add-on" is spelled A-D-D---O-N.
What does "add-on" mean?
As a noun, "add-on" means: Something which can be appended to something else.
What is the origin of the word "add-on"?
Deverbal from add on. 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.

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

Source: FrequencyWords open word-frequency list