kotatsu cover; quilt for kotatsu
A thick futon or cloth placed over the kotatsu frame to trap heat; often used together with the tabletop board.
It got cold, so I took out the kotatsu cover.
This kotatsu quilt is thick and warm.
こたつ is the heated table itself; こたつ掛け is specifically the cover or quilt placed over it.
こたつ布団 is a more common synonym for the kotatsu quilt; こたつ掛け is slightly less frequent but still widely understood.
Common mixed kana-kanji spelling; usually written in kana.
Full kanji spelling using 炬燵 for kotatsu; rare and mainly found in older or formal contexts.
Abbreviated kanji spelling omitting the okurigana け; very rare.
Alternate kanji spelling using 火燵 for kotatsu; rare.
Compound of こたつ (kotatsu, heated table) and 掛け (covering, from 掛ける 'to hang/cover'). The kanji spellings use 炬燵 or 火燵 for kotatsu, but the word is usually written in kana.