Translation guide
The English word 'prone' has two main uses: describing a physical position (lying face down) and describing a tendency or likelihood (prone to something). This guide covers both.
Describing a person or body positioned with the front or face downward.
The most common and natural way to say 'lying face down' or 'prone position'. Used as a noun or with する to mean 'lie on one's stomach'.
Don't put the baby to sleep on its stomach.
He is reading a book lying on his stomach.
Verb phrase meaning 'to lie face down' or 'to get into a prone position'.
Please lie face down during the massage.
Literally 'crawling on the belly', often used for babies or in descriptive contexts. Slightly more literary or technical than うつ伏せ.
The baby started moving on its belly.
Describing someone or something that is likely to experience something negative or has a natural inclination.
Attach to the verb stem to mean 'prone to doing' or 'easily does'. Very common and natural for tendencies, especially negative ones.
He is prone to catching colds.
This machine is prone to breaking down.
Attach to verb stem or noun to mean 'tends to' or 'is prone to', often with a negative nuance. Used for recurring states or actions.
A more formal or written expression meaning 'has a tendency to'. Used with verbs or nouns.
Means 'has a (bad) tendency to'. Used for negative habits or traits, often in critical or formal contexts.
English 'prone' can mean both 'lying face down' and 'having a tendency'. In Japanese, these are completely different expressions. Use うつ伏せ for the physical position and 〜やすい/〜がち for tendencies.
sleep on one's stomach (physical position)
prone to sleeping (tendency)
Both express tendency, but 〜やすい focuses on the ease with which something happens (often due to inherent nature), while 〜がち emphasizes frequency and often carries a negative connotation. 〜やすい can be used for positive tendencies, but 〜がち is almost always negative.
This glass breaks easily (inherent property).
She is forgetful and prone to forgetting appointments.
This area is prone to earthquakes.
He has a tendency to be late. / He is prone to being late.
He is prone to exaggerating things.
最近、ガラスが割れがちだ。
Lately, glasses have been prone to breaking (frequent occurrence).