exa-

prefix

"exa" is a 3-letter English headword indexed on PlainSpell.

The verdict

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

Unranked
below top-frequency English
4
letters

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10¹⁸ (a short scale quintillion or long scale trillion).

Corpus desk

Index EN-exa · exa- · English

exa- · unranked · 0 variants · 0 confusables

  • FREQ-UNRANKED Unranked
  • LEN-MID 4 letters
  • VOW-2 2 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-THIN "E" 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 exa-
PropertyValue
Headwordexa-
LanguageEnglish
Part of speechPrefix
Letters4
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “exa-” in English

exa-ranks outside the top 100,000 English headwords, in the long tail of specialist, archaic, or seldom-used vocabulary, exactly the territory where a reader stops mid-sentence to double-check spelling.

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

Rare enough to double-check

exa- is uncommon English outside the top frequency list, classed as aprefix. Rarity is why readers land here mid-draft. Gloss: "In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10¹⁸ (a short scale quintillion or long scale trillion).".

Zero misspellings are on record for exa- in our index, since its letter pattern doesn't lend itself to common typo substitutions. No close-neighbour confusable shows up for this headword in our dataset, since its spelling is unusual enough that it doesn't cluster with a lookalike.

Etymologically, the entry records: From Ancient Greek ἕξ (héx, “six”), for the sixth order of 10³, analogous to tera-. The correct English form is exa-, spelled E-X-A--.

Definition

  1. 1
    In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10¹⁸ (a short scale quintillion or long scale trillion).

Etymology

From Ancient Greek ἕξ (héx, “six”), for the sixth order of 10³, analogous to tera-.

Antonyms

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 "exa-"?
"exa-" is spelled E-X-A--.
What does "exa-" mean?
As a prefix, "exa-" means: In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10¹⁸ (a short scale quintillion or long scale trillion).
What is the origin of the word "exa-"?
From Ancient Greek ἕξ (héx, “six”), for the sixth order of 10³, analogous to tera-. 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