Translation guide
This guide covers how to express the idea of knowing something thoroughly in Japanese, from deep familiarity to expert-level mastery.
To express that you know a topic, place, or thing inside and out, often through experience or study.
A formal, written expression meaning to be thoroughly familiar with something. Often used in business or academic contexts.
He knows this field thoroughly.
The most common and versatile way to say you know something well. Suitable for both spoken and written Japanese.
I know this city thoroughly.
An adjective meaning knowledgeable or well-versed in a subject. Often used as 「〜に詳しい」.
He knows Japanese history thoroughly.
Implies expert-level knowledge or mastery, often used in professional or technical contexts.
She knows international law thoroughly.
Emphasizes exhaustive knowledge, often with a nuance of having explored every aspect. Can sound dramatic.
He knows this mountain thoroughly.
To express that you know someone's character, habits, or background deeply.
The standard way to say you know a person well. Works in most situations.
I know him thoroughly.
Can be used for people, but sounds more formal and is less common than for topics.
Implies knowing every detail about a person, sometimes with a nuance of intimacy or exhaustive familiarity.
To emphasize that you have full and accurate knowledge of a specific fact or detail.
Works for facts as well. Simply means you know it well.
I know that fact thoroughly.
A formal way to say you are fully aware of something, often used in business to acknowledge information.
I am thoroughly aware of that matter.
Means to grasp or have a firm understanding of a situation or information. Common in business.
I know the situation thoroughly.
To express that you have mastered a skill or memorized a process completely.
Means a skill or knowledge has become second nature through practice. Literally 'attached to the body'.
I know that technique thoroughly (it's ingrained).
Loanword from English 'master', meaning to have mastered a skill or subject.
He knows that software thoroughly.
Can also be used for processes or rules when you know them inside out.
He knows the procedure thoroughly.
熟知している is more formal and emphatic, often used in writing or speeches. よく知っている is the everyday equivalent and is safe for most situations.
Direct translations like '徹底的に知っている' are unnatural. Use the phrases above instead.
He knows the president's character thoroughly.
She knows her husband thoroughly.