separatrix

/sɛpəˈɹeɪtɹɪks/

//sɛpəˈɹeɪtɹɪks// noun

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

The verdict

“separatrix” 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
10
letters

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - The ⟨L⟩ or pipe ⟨|⟩ mark formerly used to divide integers from decimals.

Key facts for separatrix
PropertyValue
Headwordseparatrix
LanguageEnglish
Part of speechNoun
IPA/sɛpəˈɹeɪtɹɪks/
Letters10
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Where “separatrix” sits in English frequency

separatrix 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 separatrix is 10 letters long, classified as a noun, and transcribed in the International Phonetic Alphabet as /sɛpəˈɹeɪtɹɪks/. It sits outside the most-frequent rank tiers, which is often why uncommon words generate more spelling variants per reader. Wiktionary records 6 distinct senses for this headword, so context determines which meaning a reader should apply.

No misspelling variants are generated for separatrix in our index, since its letter pattern doesn't lend itself to common typo substitutions. This entry stands alone in our confusable dataset, which typically means the spelling is too distinctive to be mistaken for another word.

Etymologically, the entry records: Learned borrowing from Latin sēparātrīx, the feminine form of separator (originally owing to an implied līnea (“line”)), from sēparāre (“to divide; to separate”) + -trix (forming female agents). By surface analysis, separate + -trix. First developed as a de… The correct English form is separatrix, spelled S-E-P-A-R-A-T-R-I-X.

Definition

  1. 1
    The ⟨L⟩ or pipe ⟨|⟩ mark formerly used to divide integers from decimals.
  2. 2
    Synonym of decimal point, which replaced such marks.
  3. 3
    The proofreader's mark resembling a slash ⟨ / ⟩ or vertical bar ⟨ | ⟩ placed after a note in the margin to indicate that it should replace the item(s) struckthrough in the running text or to separate it from other margin notes.
  4. 4
    A terminator: a line on a partially-illuminated surface separating the lit and shaded regions.
  5. 5
    The line between regions having different magnetic fields.
  6. 6
    The boundary separating two modes of behavior in a differential equation.

Etymology

Learned borrowing from Latin sēparātrīx, the feminine form of separator (originally owing to an implied līnea (“line”)), from sēparāre (“to divide; to separate”) + -trix (forming female agents). By surface analysis, separate + -trix. First developed as a decimal mark among the medieval Arab mathematicians, whence a shorter variant gave rise to the decimal comma employed by many European countries and their former colonies.

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 "separatrix"?
"separatrix" is spelled S-E-P-A-R-A-T-R-I-X. The IPA pronunciation is /sɛpəˈɹeɪtɹɪks/.
What does "separatrix" mean?
As a noun, "separatrix" means: The ⟨L⟩ or pipe ⟨|⟩ mark formerly used to divide integers from decimals.
How do you pronounce "separatrix"?
The IPA (International Phonetic Alphabet) transcription for "separatrix" is /sɛpəˈɹeɪtɹɪks/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "separatrix"?
Learned borrowing from Latin sēparātrīx, the feminine form of separator (originally owing to an implied līnea (“line”)), from sēparāre (“to divide; to separate”) + -trix (forming female agents). By surface analysis, separate + -trix. First develop... 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 “separatrix”

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

  • The one correct English spelling is S-E-P-A-R-A-T-R-I-X - every other letter order is a misspelling in standard orthography.
  • Say it as /sɛpəˈɹeɪtɹɪks/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
  • 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