non compos mentis

adj

"non-compos-mentis" is a 15-letter English headword indexed on PlainSpell.

The verdict

“non compos mentis” is uncommon English (outside the top frequency list), classed as an adjective. The kind of spelling people second-guess.

Unranked
below top-frequency English
17
letters

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - Insane; not of sound mind; not in control of oneself.

Corpus desk

Index EN-non-compos-mentis · non compos mentis · English

non compos mentis · unranked · 0 variants · 0 confusables

  • FREQ-UNRANKED Unranked
  • LEN-MEGA 17 letters
  • VOW-5 5 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-THIN "N" 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 non compos mentis
PropertyValue
Headwordnon compos mentis
LanguageEnglish
Part of speechAdjective
Letters17
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “non compos mentis” in English

non compos mentissits 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

non compos mentis is uncommon English outside the top frequency list, classed as anadjective. Rarity is why readers land here mid-draft. Gloss: "Insane; not of sound mind; not in control of oneself.".

Zero misspellings are on record for non compos mentis in our index, and the word's spelling is regular enough that our generator found nothing worth flagging. It is not paired with a close-neighbour confusable in our dataset, which tends to mean the word is visually distinctive enough to stand on its own.

Etymologically, the entry records: From Latin non (“not”) + compos (“in control, having mastery”) + mentis (“of mind”). The correct English form is non compos mentis, spelled N-O-N- -C-O-M-P-O-S- -M-E-N-T-I-S.

Definition

  1. 1
    Insane; not of sound mind; not in control of oneself.

Etymology

From Latin non (“not”) + compos (“in control, having mastery”) + mentis (“of mind”).

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 "non compos mentis"?
"non compos mentis" is spelled N-O-N- -C-O-M-P-O-S- -M-E-N-T-I-S.
What does "non compos mentis" mean?
As an adjective, "non compos mentis" means: Insane; not of sound mind; not in control of oneself.
What is the origin of the word "non compos mentis"?
From Latin non (“not”) + compos (“in control, having mastery”) + mentis (“of mind”). 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