sharpen
sharp + -en
https://gyazo.com/17bd3be08bd1391250ea2acd3566b461
verb
1. make or become sharp or sharper:
〈物〉を鋭くする, 研ぐ, とがらせる
e.g. with object : she sharpened her pencil
〈刃物･鉛筆などが〉鋭くなる
e.g. no object : her tone sharpened.
2. (sharpen up or sharpen something up) improve or cause to improve:
〈技術〉を磨く, 高める, 〈感覚･理解力〉を鋭敏にする(up)
e.g. they've got to sharpen up in front of the goal
e.g. students will sharpen up their reading skills.
3. with object Music British raise the pitch of (a note) by a semitone.