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.
sharpen a knife
sharpen a pencil
sharpen a skill
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.
I sharpen the kitchen knife.
He sharpens his razor every morning.
Used specifically for sharpening pencils by shaving off wood. Not for blades.
An alternative kanji for 研ぐ, also meaning to sharpen on a whetstone. Less common in everyday use.
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.
To refine or improve an ability, sense, or technique through practice.
Literally 'to polish', used metaphorically for refining skills, senses, or talents.
To make a feeling, appetite, or attention more acute.
A phrase meaning 'to make sharp/keen', used for senses, pain, or focus.
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.
Sharpen a kitchen knife.
I need to sharpen this knife; it's too dull.
Natural Japanese uses 研ぐ for knife sharpening.
I sharpen a pencil.
Sharpen a sword.
Please sharpen the pencil.
I sharpen a pencil with a pencil sharpener.
Sharpen one's skills.
He is sharpening his language skills.
Can be used metaphorically for sharpening senses or intuition, though less common than 磨く for skills.
Sharpen one's senses.
Means 'to forge/train', used for strengthening or disciplining abilities, often physical or mental.
Sharpen one's judgment.
The pain sharpened his senses.
He sharpened his attention.
Used for stimulating appetite or curiosity. Often in the form 食欲をそそる (sharpen one's appetite).
The smell sharpened my appetite.
鉛筆を削る。
Sharpen a pencil.
Sharpen one's talent.
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.
She sharpened her pencil before the exam.
He practices daily to sharpen his skills.