Translation guide
The English verb 'deepen' can be used for physical depth, intensifying abstract qualities, or making something more profound. In Japanese, there is no single direct equivalent; the translation depends heavily on the context. This guide covers the most common ways to express these ideas naturally.
To increase the physical depth of something, such as a hole, a river, or a container.
The most straightforward way to say 'make deeper'. It uses the adjective 深い (deep) in its adverbial form 深く plus する (to do/make).
Construction work to deepen the river has begun.
Please make the hole a little deeper.
Literally 'dig down', used when deepening by digging, such as a hole or a trench. It can also be used metaphorically for delving into a topic.
We need to deepen the well.
A transitive verb meaning 'to deepen', but it is rarely used for physical depth. It is more common in abstract contexts (see next meaning). Using it for physical depth can sound literary or unusual.
Avoid using 深める for physical depth in everyday speech; use 深くする instead.
Deepen the bottom of the pond. (literary/technical)
To make a feeling, relationship, understanding, color, or other abstract quality stronger or more intense.
The most common transitive verb for abstract deepening. It is used with nouns like 理解 (understanding), 関係 (relationship), 絆 (bonds), 知識 (knowledge), etc.
It is important to deepen mutual understanding.
Means 'to strengthen' or 'intensify'. It is used when 'deepen' implies making something more powerful or pronounced, such as a color, impression, or suspicion.
Intransitive verb meaning 'to deepen' (become deeper). Use this when the subject itself deepens, not when someone deepens something.
A more analytical phrase using 深くする, similar to the physical meaning but applied to abstract nouns. It is less common than 深める but still natural.
A formal, technical term meaning 'to deepen' or 'to intensify', often used in academic or business contexts. It is a Sino-Japanese compound (深化 + させる).
To make a voice or sound deeper, as in lower pitch.
To become deeper in a physical or abstract sense, without an agent causing it.
The most common intransitive expression for physical or abstract deepening. It uses the adjective 深い (deep) in its adverbial form 深く plus なる (to become).
The river deepened due to the rain.
His knowledge is deepening day by day.
Intransitive verb meaning 'to deepen', often used for abstract things like seasons, relationships, or understanding. It implies a natural progression.
深める (fukameru) is transitive (someone deepens something), while 深まる (fukamaru) is intransitive (something deepens on its own). Choose based on whether there is a direct object.
Do not assume 'deepen' can always be translated as 深める. For physical depth, 深くする is more natural. For intensifying colors or sounds, 強める or 低くする may be better.
We went on a trip to deepen our friendship.
疑惑を強める発言だった。
It was a remark that deepened the suspicion.
I added paint to deepen the color.
秋が深まるにつれて、紅葉が美しくなる。
As autumn deepens, the leaves become more beautiful.
The bond between the two deepened.
I continue studying to deepen my knowledge.
It is necessary to deepen the cooperative relationship between the two countries.
Lower/deepen the tone of one's voice.
秋が深まる。
Autumn deepens.