cosine

/ˈkəʊ.saɪn/

//ˈkəʊ.saɪn// noun

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

"cosine" is a 6-letter English headword indexed on PlainSpell.

The verdict

“cosine” is uncommon English (frequency #52,240 among 5,599 “C” headwords), classed as a noun. The kind of spelling people second-guess.

#52,240
frequency rank, English
5,599
“C” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - In a right triangle, the ratio of the length of the side adjacent to an acute angle to the length of the hypotenuse. Symbol: cos

Corpus desk

Index EN-cosine · cosine · English

cosine · rank #52,240 · 0 variants · 0 confusables

  • FREQ-RARE #52,240
  • LEN-LONG 6 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-DENSE 5,599
  • PHOTO-FINISH cosmonaut

Nearest frequency peer: cosmonaut (+1 rank slots)

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.

Long-tail ranks near “cosine”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

What this shows Long-tail view: where “cosine” sits against similarly uncommon English ranks.

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for cosine
PropertyValue
Headwordcosine
LanguageEnglish
Part of speechNoun
IPA/ˈkəʊ.saɪn/
Letters6
Frequency rank#52,240
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “cosine” in English

This scale runs from the tiny cluster of words that carry ordinary speech (left) to the long tail of words almost nobody reaches for (right).cosinefalls in this rarity band:

#1#100#1K#10K#100K
← used constantlyrarely used →

Ticks step logarithmically, so each one marks a roughly tenfold drop in how often the word turns up. Rare peers in the same band: “cosmonaut” (#52,241), “copywriter” (#52,237), “Cottrell” (#52,243). Among 5,599 “C” headwords, “cosine” is #52,240. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

cosine is uncommon English at frequency #52,240 among 5,599 “C” headwords, classed as anoun, transcribed /ˈkəʊ.saɪn/. Rarity is why readers land here mid-draft. Gloss: "In a right triangle, the ratio of the length of the side adjacent to an acute angle to the length of the hypotenuse. Symbol: cos".

cosine has no tracked misspelling variants, suggesting the orthography follows predictable English patterns. This headword has no recorded confusable partner, a sign it's visually distinctive enough not to be mixed up with another word.

Etymologically, the entry records: From co- + sine, short for complementi sinus in Latin, meaning “sine of the complement”. Doublet of cosinus. The correct English form is cosine, spelled C-O-S-I-N-E.

Definition

  1. 1
    In a right triangle, the ratio of the length of the side adjacent to an acute angle to the length of the hypotenuse. Symbol: cos

Etymology

From co- + sine, short for complementi sinus in Latin, meaning “sine of the complement”. Doublet of cosinus.

This word in other languages

coseno(Español)cosinus(Français)Kosinus(Deutsch)

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "cosine"?
"cosine" is spelled C-O-S-I-N-E. The IPA pronunciation is /ˈkəʊ.saɪn/.
What does "cosine" mean?
As a noun, "cosine" means: In a right triangle, the ratio of the length of the side adjacent to an acute angle to the length of the hypotenuse. Symbol: cos
How do you pronounce "cosine"?
The IPA (International Phonetic Alphabet) transcription for "cosine" is /ˈkəʊ.saɪn/. 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 "cosine"?
From co- + sine, short for complementi sinus in Latin, meaning “sine of the complement”. Doublet of cosinus. 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.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "cosine", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 6 letters (nearest by frequency rank).

curler#52,252deejay#52,259defund#52,262Cheeto#52,215

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list