noun, noun which may take the genitive case particle 'no'
slit; narrow gap; interstice
Refers to a very narrow opening or crack, often in a physical object or structure. Can be used as a noun or with の to modify another noun.
Light was leaking through a slit in the wall.
I peered inside through the narrow gap.
Compound of 細 (さい, 'thin, narrow') and 隙 (げき, 'gap, crevice'). The reading is on'yomi, and the word is used in formal or technical contexts.