litmus test

noun

"litmus-test" is a 10-letter English headword indexed on PlainSpell.

The verdict

“litmus test” is outside the top-ranked English vocabulary, used as a noun - the kind of word writers most often double-check.

Unranked
below top-frequency English
11
letters

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - A simple, binary test for the acidity or alkalinity of a substance, using litmus paper.

Key facts for litmus test
PropertyValue
Headwordlitmus test
LanguageEnglish
Part of speechNoun
Letters11
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Where “litmus test” sits in English frequency

litmus test 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 litmus test is 11 letters long, classified as a noun. 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.

We couldn't generate a plausible misspelling set for litmus test, suggesting the orthography follows predictable English patterns. Our dataset records no confusable match here, since nothing in our dataset looks or sounds close enough to cause mix-ups.

Etymologically, the entry records: From litmus + test. The correct English form is litmus test, spelled L-I-T-M-U-S- -T-E-S-T.

Definition

  1. 1
    A simple, binary test for the acidity or alkalinity of a substance, using litmus paper.
  2. 2
    Any test which produces a binary, decisive result (for example, determining whether to appoint someone to a job) by measuring a single indicator.

Etymology

From litmus + test.

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 "litmus test"?
"litmus test" is spelled L-I-T-M-U-S- -T-E-S-T.
What does "litmus test" mean?
As a noun, "litmus test" means: A simple, binary test for the acidity or alkalinity of a substance, using litmus paper.
What is the origin of the word "litmus test"?
From litmus + test. 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 “litmus test”

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

  • The one correct English spelling is L-I-T-M-U-S- -T-E-S-T - 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