Translation guide
Describing something as very thin in English can refer to physical thinness of objects, people, or materials, as well as metaphorical thinness like sparse attendance or weak arguments. Japanese uses different words depending on what is thin and the degree of thinness.
Describing something that is very thin in thickness, such as paper, cloth, a slice of meat, or a thin wall.
The most common word for 'thin' (of flat objects). Can be intensified with adverbs like とても or すごく.
この紙はとても薄い。
This paper is very thin.
壁が薄くて、隣の音が聞こえる。
The walls are very thin, so I can hear the neighbors.
Means 'ultra-thin' or 'extremely thin'. Often used in product descriptions (e.g., condoms, slices of meat).
極薄のスライス肉を買った。
I bought ultra-thin sliced meat.
Onomatopoeic word for something flimsy and thin, like cheap paper or thin fabric. Often has a negative nuance of being flimsy or lacking substance.
この布はペラペラで、すぐ破れそう。
This cloth is very thin and looks like it will tear easily.
Describing a person or body part that is very slender or skinny, often with a nuance of being too thin.
Used for long, slender things like arms, legs, fingers, or a person's build. Can be neutral or positive (slender) but can also imply 'too thin' depending on context.
彼女は腕がとても細い。
She has very thin arms.
あのモデルは細すぎる。
That model is too thin.
Means 'thin' in the sense of being skinny or underweight. Often used for people or animals. Can be intensified with とても.
彼は病気でとても痩せている。
He is very thin because of illness.
Onomatopoeic word meaning 'skinny' or 'bony', often with a negative connotation of being unhealthily thin. Very casual.
Describing something that is thin in the sense of being watery, sparse, or not dense.
Also used for liquids (weak/watery), fog (thin/light), hair (thin/sparse), etc. The same word as for flat objects, but context distinguishes meaning.
このスープは味が薄い。
This soup is very thin (watery/weak in flavor).
彼は髪が薄くなってきた。
His hair has become very thin.
Means 'sparse' or 'thin' in the sense of being scattered or not dense, used for hair, crowd, vegetation, etc.
Describing an argument, excuse, or evidence that is flimsy or not convincing.
Literally 'persuasive power is thin', meaning unconvincing or weak.
彼の言い訳は説得力が薄い。
His excuse is very thin (unconvincing).
Formal word meaning 'weak' or 'flimsy', often used in compounds like 根拠薄弱 (groundless).
その主張は根拠が薄弱だ。
That claim is based on very thin evidence.
薄い (usui) is for flat things (paper, walls) or density (soup, fog, hair). 細い (hosoi) is for long, slender things (arms, legs, fingers, a person's build). Do not use 薄い for a thin person; use 細い or 痩せている.
While 薄い can be used metaphorically, a direct translation like '薄い言い訳' is not natural. Use 説得力が薄い or 薄弱な言い訳 instead.
あの犬はガリガリだ。
That dog is very thin (bony).
The audience was very thin (sparse).