Vocabulary
Form
to sharpen; to hone; to whet; to grind
verb
vt
N1
freq #42
Example sentences
彼（かれ）はナイフを研（と）いでいました。
He was sharpening a knife.
猫（ねこ）が柱（はしら）でつめを研（と）いでいた。
A cat was sharpening its claws against a post.