# sill

> English word · Noun · IPA /sɪl/ · frequency rank #29,086

## Definitions
1. A breast wall; window breast; horizontal brink which forms the base of a window.
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. A stratum of rock, especially an intrusive layer of igneous rock lying parallel to surrounding strata.
4. A threshold or brink across the bottom of a canal lock for the gates to shut against.
5. A raised area at the base of the nasal aperture in the skull.
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).

## Easily confused with
- **SL** (https://plainspell.com/en/vs/sill-vs-sl)
- **six** (https://plainspell.com/en/vs/sill-vs-six)
- **sir** (https://plainspell.com/en/vs/sill-vs-sir)
- **sit** (https://plainspell.com/en/vs/sill-vs-sit)
- **sin** (https://plainspell.com/en/vs/sill-vs-sin)
- **SIM** (https://plainspell.com/en/vs/sill-vs-sim)
- **sol** (https://plainspell.com/en/vs/sill-vs-sol)
- **sip** (https://plainspell.com/en/vs/sill-vs-sip)
- **sis** (https://plainspell.com/en/vs/sill-vs-sis)
- **sly** (https://plainspell.com/en/vs/sill-vs-sly)
- **SQL** (https://plainspell.com/en/vs/sill-vs-sql)
- **SNL** (https://plainspell.com/en/vs/sill-vs-snl)
- **SLR** (https://plainspell.com/en/vs/sill-vs-slr)
- **Sul** (https://plainspell.com/en/vs/sill-vs-sul)
- **Siu** (https://plainspell.com/en/vs/sill-vs-siu)
- **SLC** (https://plainspell.com/en/vs/sill-vs-slc)
- **SLA** (https://plainspell.com/en/vs/sill-vs-sla)
- **SPL** (https://plainspell.com/en/vs/sill-vs-spl)
- **SLE** (https://plainspell.com/en/vs/sill-vs-sle)
- **site** (https://plainspell.com/en/vs/sill-vs-site)

## Common misspellings (3)
`isll`, `slil`, `ssill`

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/sill