Translation guide
A large rock, typically one that has been rounded by natural processes. In Japanese, the most common word is 岩 (iwa), but to emphasize size, you can use 巨石 (kyoseki) or 大岩 (ōiwa). For specific contexts like climbing, ボルダー (borudā) is used.
Referring to a large, natural rock, often rounded, found in nature or used in landscaping.
The most common word for 'rock' or 'boulder'. It can refer to rocks of various sizes, but context usually makes it clear if it's large.
大きな岩が道をふさいでいた。
A large boulder was blocking the road.
庭に岩を置いた。
I placed a boulder in the garden.
Literally 'giant rock', this explicitly means a very large rock or boulder. More formal or literary.
その巨石は古代の遺跡の一部だ。
That boulder is part of an ancient ruin.
A compound meaning 'big rock'. Common in everyday speech when you want to emphasize size.
あの大岩に登ってみよう。
Let's try climbing that boulder.
A more technical term for 'rock' in general, often used in geology. Can refer to boulders in scientific contexts.
この地域には巨大な岩石が多い。
There are many huge boulders in this area.
Specifically referring to a boulder used in bouldering, a form of rock climbing.
Loanword from English, used almost exclusively in the context of bouldering. Refers to the climbing problem or the rock itself.
このボルダーは難易度が高い。
This boulder is high in difficulty.
ジムで新しいボルダーに挑戦した。
I tried a new boulder at the gym.
In climbing contexts, 岩 can also mean boulder, especially when referring to outdoor natural boulders.
Using 'boulder' metaphorically to describe something large, heavy, or immovable.
Means 'like a boulder/rock', used to describe something massive, solid, or unyielding.
彼は岩のような男だ。
He is a man like a boulder (solid and dependable).
岩のような沈黙が続いた。
A boulder-like silence continued.
岩 (iwa) generally refers to larger rocks or boulders, while 石 (ishi) refers to smaller stones or pebbles. If you can hold it in one hand, it's probably 石; if it's too large to lift, it's 岩.
道に石が落ちていた。
A stone was lying on the road.
道に岩が落ちていた。
A boulder was lying on the road.
大岩 (ōiwa) is more colloquial and commonly used in everyday speech, while 巨石 (kyoseki) sounds more formal or literary. For most situations, 大きな岩 (ōkina iwa) is perfectly natural.
I go bouldering on outdoor boulders.