noun
lintel; upper door frame
In Japanese architecture, specifically the horizontal beam at the top of a sliding door frame, often grooved to guide sliding doors (fusuma or shoji). Contrasts with 敷居 (threshold/sill).
See also: 敷居
鴨居に埃がたまっている。
Dust has accumulated on the lintel.
この鴨居は古くて、襖が滑りにくい。
This lintel is old, and the sliding door doesn't slide smoothly.
敷居 is the threshold or sill at the bottom of a door frame, while 鴨居 is the lintel at the top. Together they form the frame for sliding doors.
The origin of the word is uncertain. The kanji 鴨 (wild duck) and 居 (reside) are ateji, chosen for their sounds rather than meaning.