Translation guide
The English adverb 'thoroughly' means doing something completely, in great detail, or to a very high degree. In Japanese, there is no single direct equivalent; instead, various adverbs, verb forms, and expressions are used depending on the nuance.
Expressing that an action is done fully, leaving nothing out, or covering all aspects.
The most direct equivalent for 'thoroughly' in the sense of doing something exhaustively and systematically. Often used for investigations, cleaning, preparations, etc.
The police thoroughly investigated the case.
He studied thoroughly for the exam.
Means 'completely' or 'entirely', often implying a change of state or that nothing is left. Used for forgetting, finishing, becoming dark, etc.
I've thoroughly forgotten his name.
I cleaned the room thoroughly.
Means 'sufficiently' or 'enough', but can be used for 'thoroughly' when emphasizing that something is done to a satisfactory degree.
Please cook the meat thoroughly.
Literally 'without nooks', meaning 'everywhere, all over, thoroughly'. Used for searching or covering an area completely.
The police thoroughly searched the forest.
Emphasizing the extent or intensity of an adjective or verb, similar to 'really' or 'completely'.
Common intensifier meaning 'really' or 'truly'. Can replace 'thoroughly' when it means 'very'.
That's a thoroughly interesting book.
Means 'completely' or 'entirely', often used with negative or extreme statements. Can sound emphatic.
Formal intensifier meaning 'very' or 'extremely'. Suitable for written or formal contexts.
Focusing on the carefulness and attention to detail in performing an action.
Means 'carefully', 'elaborately', or 'with great attention to detail'. Often used for preparations, cleaning, or checking.
She thoroughly planned the trip.
Means 'minutely', 'in detail'. Used when breaking something down or examining it thoroughly.
He thoroughly analyzed the problem.
There is no single Japanese adverb that covers all uses of 'thoroughly'. Using 徹底的に for every case can sound unnatural. Choose the expression that matches the nuance: completeness, intensity, or carefulness.
徹底的に implies a systematic, exhaustive process (e.g., investigation, study). すっかり implies a complete change of state or that nothing remains (e.g., forgetting, finishing). Using すっかり for an active, detailed process can sound odd.
I thoroughly enjoyed the party.
Here 'thoroughly' is an intensifier, so 本当に is natural.
Please wash the vegetables thoroughly.
十分に emphasizes doing it enough to be safe/clean.
彼の説明はまったく理解できなかった。
I thoroughly failed to understand his explanation.
その問題は非常に難しい。
That problem is thoroughly difficult.