Translation guide
The English verb 'sharpen' covers making something sharp (knives, pencils), honing skills, and intensifying sensations or focus. Japanese uses different verbs depending on what is being sharpened.
To make a knife, scissors, or other cutting tool sharp by grinding or whetting.
The most common verb for sharpening blades, especially kitchen knives. Implies using a whetstone or similar tool.
包丁を研ぐ。
I sharpen the kitchen knife.
彼は毎朝剃刀を研いでいる。
He sharpens his razor every morning.
Used specifically for sharpening pencils by shaving off wood. Not for blades.
鉛筆を削る。
I sharpen a pencil.
An alternative kanji for 研ぐ, also meaning to sharpen on a whetstone. Less common in everyday use.
刀を砥ぐ。
Sharpen a sword.
To make the tip of a pencil pointed using a sharpener or knife.
The standard verb for sharpening pencils. Can be used with a pencil sharpener or a knife.
鉛筆を削ってください。
Please sharpen the pencil.
鉛筆削りで鉛筆を削る。
I sharpen a pencil with a pencil sharpener.
To refine or improve an ability, sense, or technique through practice.
Literally 'to polish', used metaphorically for refining skills, senses, or talents.
技術を磨く。
Sharpen one's skills.
彼は語学力を磨いている。
He is sharpening his language skills.
Can be used metaphorically for sharpening senses or intuition, though less common than 磨く for skills.
感覚を研ぐ。
Sharpen one's senses.
Means 'to forge/train', used for strengthening or disciplining abilities, often physical or mental.
To make a feeling, appetite, or attention more acute.
A phrase meaning 'to make sharp/keen', used for senses, pain, or focus.
痛みが感覚を鋭くした。
The pain sharpened his senses.
彼は注意を鋭くした。
He sharpened his attention.
Used for stimulating appetite or curiosity. Often in the form 食欲をそそる (sharpen one's appetite).
研ぐ (togu) is for blades using a whetstone. 削る (kezuru) is for pencils by shaving. 磨く (migaku) is for polishing surfaces or refining skills. Do not use 削る for knives or 研ぐ for pencils.
English 'sharpen' can be used broadly (sharpen a stick, sharpen focus), but Japanese verbs are more specific. Avoid directly translating 'sharpen' as 鋭くする for physical objects; it sounds unnatural.
この包丁を研がないと。切れ味が悪すぎる。
I need to sharpen this knife; it's too dull.
Natural Japanese uses 研ぐ for knife sharpening.
彼女は試験前に鉛筆を削った。
She sharpened her pencil before the exam.
彼は技術を磨くために毎日練習している。
He practices daily to sharpen his skills.
判断力を鍛える。
Sharpen one's judgment.
The smell sharpened my appetite.