sinus

/ˈsaɪ.nəs/

//ˈsaɪ.nəs// noun

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

"sinus" is a 5-letter English headword indexed on PlainSpell.

The verdict

“sinus” is a moderately-common English word, ranked #20,225 in English word frequency and used as a noun.

#20,225
frequency rank, English
5
letters
7
tracked misspellings
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - A pouch or cavity in a bone or other tissue, especially one in the bones of the face or skull connecting with the nasal cavities (the paranasal sinus).

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

sinus vs sis
60% similar
sinus vs Sus
40% similar
sinus vs Siu
40% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for sinus
PropertyValue
Headwordsinus
LanguageEnglish
Part of speechNoun
IPA/ˈsaɪ.nəs/
Letters5
Frequency rank#20,225
Misspellings tracked7
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “sinus” sits in English frequency

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right). sinus lands here:

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

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

Spelling & Dictionary Insight

The English entry for sinus is 5 letters long, classified as a noun, and transcribed in the International Phonetic Alphabet as /ˈsaɪ.nəs/. Corpus data places it at rank #20,225 in overall English word frequency, marking it as uncommon enough that many writers pause before typing it. Wiktionary records 7 distinct senses for this headword, so context determines which meaning a reader should apply.

Our generated misspelling index lists 7 likely wrong-spelling variants for sinus, with forms such as "isnus", "sinnus", and "sinsu". Every one of these variants traces to a single-character edit -- an added or dropped letter, a swapped consonant, or a vowel swap -- the kind of slip a spell-checker is built to catch. It also participates in 20 confusable-pair relationships, "sis", "Sus", "Siu", and more, where similar look or sound leads writers to substitute one word for another in context.

Etymologically, the entry records: Learned borrowing from Latin sinus (“a bent surface, curve, hollow”). Doublet of sine. The correct English form is sinus, spelled S-I-N-U-S.

Definition

  1. 1
    A pouch or cavity in a bone or other tissue, especially one in the bones of the face or skull connecting with the nasal cavities (the paranasal sinus).
  2. 2
    An irregular venous or lymphatic cavity, reservoir, or dilated vessel.
  3. 3
    An irregular venous or lymphatic cavity, reservoir, or dilated vessel.
  4. 4
    An abnormal cavity or passage such as a fistula, leading from a deep-seated infection and discharging pus to the surface.
  5. 5
    A rounded notch or depression between two lobes or teeth in the margin of a leaf or petal.
  6. 6
    A bay of the sea; a recess in the shore.
  7. 7
    Synonym of sine.

Etymology

Learned borrowing from Latin sinus (“a bent surface, curve, hollow”). Doublet of sine.

This word in other languages

seno(Español)sinus(Français)Sinus(Deutsch)seio(Português)

Common misspellings

Also misspelled as: isnus,sinnus,sinsu,sinuss,siuns,snius,ssinus

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of sinus - measured in single-character edits (insert, delete, or substitute a letter). Larger bars are easier to catch; one-edit slips are the sneakiest.

isnus2sinnus1sinsu2sinuss1siuns2snius2ssinus1
Edit distance from "sinus"

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 "sinus"?
"sinus" is spelled S-I-N-U-S. The IPA pronunciation is /ˈsaɪ.nəs/.
What does "sinus" mean?
As a noun, "sinus" means: A pouch or cavity in a bone or other tissue, especially one in the bones of the face or skull connecting with the nasal cavities (the paranasal sinus).
What words are commonly confused with "sinus"?
"sinus" is commonly confused with "sis", "Sus", "Siu". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "sinus"?
The IPA (International Phonetic Alphabet) transcription for "sinus" is /ˈsaɪ.nəs/. 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 "sinus"?
Learned borrowing from Latin sinus (“a bent surface, curve, hollow”). Doublet of sine. 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 “sinus”

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

  • The one correct English spelling is S-I-N-U-S - every other letter order is a misspelling in standard orthography.
  • Say it as /ˈsaɪ.nəs/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
  • Don't mix it up with “sis” - see the side-by-side comparison. sinus vs sis
  • 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