sill

/sɪl/

//sɪl// noun

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

"sill" is a 4-letter English headword indexed on PlainSpell.

The verdict

“sill” is a moderately-common English word, ranked #29,086 in English word frequency and used as a noun.

#29,086
frequency rank, English
4
letters
3
tracked misspellings
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - A breast wall; window breast; horizontal brink which forms the base of a window.

Visual similarity to commonly confused words

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

sill vs SL
0% similar
sill vs six
50% similar
sill vs sir
50% similar

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

Key facts for sill
PropertyValue
Headwordsill
LanguageEnglish
Part of speechNoun
IPA/sɪl/
Letters4
Frequency rank#29,086
Misspellings tracked3
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “sill” 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). sill 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 sill is 4 letters long, classified as a noun, and transcribed in the International Phonetic Alphabet as /sɪl/. Corpus data places it at rank #29,086 in overall English word frequency, marking it as uncommon enough that many writers pause before typing it. Wiktionary records 6 distinct senses for this headword, so context determines which meaning a reader should apply.

Our generated misspelling index lists 3 likely wrong-spelling variants for sill, with forms such as "isll", "slil", and "ssill". Each of these forms differs from the correct spelling by one small edit: a doubled letter, a dropped silent letter, or a substituted vowel. It also participates in 20 confusable-pair relationships, "SL", "six", "sir", and more, a pairing that trips writers up because the two words share enough sound or shape to blur together.

Etymologically, the entry records: From Middle English sille, selle, sülle, from Old English syll, syl (“sill, threshold, foundation, base, basis”), from Proto-Germanic *sulī (“bar, sill”), from Proto-Indo-European *sel-, *swel- (“beam, board, frame, threshold”). Cognate with Scots sil, sill… The correct English form is sill, spelled S-I-L-L.

Definition

  1. 1
    A breast wall; window breast; horizontal brink which forms the base of a window.
  2. 2
    A threshold; horizontal structural member of a building near ground level on a foundation or pilings, or lying on the ground, and bearing the upright portion of a frame; a sill plate.
  3. 3
    A stratum of rock, especially an intrusive layer of igneous rock lying parallel to surrounding strata.
  4. 4
    A threshold or brink across the bottom of a canal lock for the gates to shut against.
  5. 5
    A raised area at the base of the nasal aperture in the skull.
  6. 6
    The inner edge of the bottom of an embrasure.

Etymology

From Middle English sille, selle, sülle, from Old English syll, syl (“sill, threshold, foundation, base, basis”), from Proto-Germanic *sulī (“bar, sill”), from Proto-Indo-European *sel-, *swel- (“beam, board, frame, threshold”). Cognate with Scots sil, sill (“balk, beam, floor, sill”), Dutch zulle (“sill”), Low German Sull, Sülle (“threshold, ramp, sill”), German Süll, Sülle (“threshold, sill”), Danish syld (“base of a framework building”), Swedish syll (“joist, cross-tie”), Norwegian syll, Icelandic syll, sylla (“sill”). Related also to German Schwelle ( > Danish svelle), Old Norse svill, Latin silva (“wood, forest”), Ancient Greek ὕλη (húlē).

This word in other languages

alféizar(Español)rebord(Français)Fensterbank(Deutsch)parapeito(Português)

Common misspellings

Also misspelled as: isll,slil,ssill

Misspelling Pattern Breakdown

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

isll2slil2ssill1
Edit distance from "sill"

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 "sill"?
"sill" is spelled S-I-L-L. The IPA pronunciation is /sɪl/.
What does "sill" mean?
As a noun, "sill" means: A breast wall; window breast; horizontal brink which forms the base of a window.
What words are commonly confused with "sill"?
"sill" is commonly confused with "SL", "six", "sir". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "sill"?
The IPA (International Phonetic Alphabet) transcription for "sill" is /sɪl/. 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 "sill"?
From Middle English sille, selle, sülle, from Old English syll, syl (“sill, threshold, foundation, base, basis”), from Proto-Germanic *sulī (“bar, sill”), from Proto-Indo-European *sel-, *swel- (“beam, board, frame, threshold”). Cognate with Scots... 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 “sill”

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

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