ex post facto

adj

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

"ex-post-facto" is a 11-letter English headword indexed on PlainSpell.

The verdict

“ex post facto” is outside the top-ranked English vocabulary, used as an adjective - the kind of word writers most often double-check.

Unranked
below top-frequency English
13
letters

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Retroactive.

Key facts for ex post facto
PropertyValue
Headwordex post facto
LanguageEnglish
Part of speechAdjective
Letters13
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Where “ex post facto” sits in English frequency

ex post facto 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 ex post facto is 13 letters long, classified as an adjective. It sits outside the most-frequent rank tiers, which is often why uncommon words generate more spelling variants per reader. Wiktionary records 2 distinct senses for this headword, so context determines which meaning a reader should apply.

The misspelling generator found no plausible variants for ex post facto, and the word's spelling is regular enough that our generator found nothing worth flagging. We don't track a confusable pairing for this entry, since its spelling is unusual enough that it doesn't cluster with a lookalike.

Etymologically, the entry records: From Latin ex (“from”) + post (“after”) + facto, ablative of factum (“deed”). In Latin, ex takes the ablative case, while post takes the accusative case. (See Wikipedia for a discussion of the grammatical form and usage of this phrase.) The correct English form is ex post facto, spelled E-X- -P-O-S-T- -F-A-C-T-O.

Definition

  1. 1
    Retroactive.
  2. 2
    Retroactive.

Etymology

From Latin ex (“from”) + post (“after”) + facto, ablative of factum (“deed”). In Latin, ex takes the ablative case, while post takes the accusative case. (See Wikipedia for a discussion of the grammatical form and usage of this phrase.)

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 "ex post facto"?
"ex post facto" is spelled E-X- -P-O-S-T- -F-A-C-T-O.
What does "ex post facto" mean?
As an adjective, "ex post facto" means: Retroactive.
What is the origin of the word "ex post facto"?
From Latin ex (“from”) + post (“after”) + facto, ablative of factum (“deed”). In Latin, ex takes the ablative case, while post takes the accusative case. (See Wikipedia for a discussion of the grammatical form and usage of this phrase.) 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.

Using “ex post facto”

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

  • The one correct English spelling is E-X- -P-O-S-T- -F-A-C-T-O - 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