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” has 7 generated spelling variants in the English index at frequency #20,225. The variants make it a useful spelling check.

#20,225
frequency rank, English
6,566
“S” headwords
7
tracked misspellings
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed September 3, 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).

Corpus desk

Index EN-sinus · sinus · English

sinus · rank #20,225 · 7 variants · 20 confusables

  • FREQ-MID #20,225
  • LEN-MID 5 letters
  • VOW-2 2 vowels
  • CONFUS-HIGH 20 pairs
  • VAR-MID 7 variants
  • BOOK-DENSE 6,566
  • PHOTO-FINISH situ

Nearest frequency peer: situ (+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.

Rank peers near misspelling magnet “sinus”

Same rarity band: useful when a typo lands on a peer headword

corpus weight

What this shows “sinus” sits among these FrequencyWords peers; misspelling depth is tracked separately in the edit-distance chart.

Source FrequencyWords open word-frequency list As of September 3, 2026

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)

Frequency seat of misspelling magnet “sinus”

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).sinuslands here:

#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. Same rarity band neighbours include “situ” (#20,226), “skid” (#20,227), “shabby” (#20,222). Among 6,566 “S” headwords, “sinus” is #20,225. Source: FrequencyWords open word-frequency list.

A misspelling magnet

The generator records 7 spelling variants around sinus (IPA /ˈsaɪ.nəs/), anoun. Corpus frequency is #20,225 among 6,566 “S” headwords. Wiktionary lists 7 senses, so context still picks the gloss.

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.

Recorded use

Wiktionary examples

These source excerpts show how sinus appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. So, in the helicopteron, as the helix is at the same time a sustaining plane, it should be likened to a surface moving horizontally, and in which, consequenty, the resistance to motion will be to the lifting power as the sinus is to the cosinus of the angle formed by such plane with the horizon.
  2. The variations are described in terms of cycles of sinuses and cosinuses.

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.

Similar English words by spelling shape

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

Same letter count

Frequency-ranked English headwords with 5 letters (nearest by frequency rank).

stung#20,239Rhine#20,210waldo#20,263whine#20,267

Similar misspelling depth

Headwords with a similar count of attested misspellings (7 here; floor ≥5).

waller7 variantsabort7 variantsAmish7 variantsbanjo7 variants

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

Source: FrequencyWords open word-frequency list