Translation guide
The English adverb "sufficiently" means "to an adequate degree" or "enough." In Japanese, this concept is most naturally expressed using adverbs like 十分に (じゅうぶんに) or the verb 足りる (たりる). The best choice depends on whether you are modifying an adjective, a verb, or describing a state.
Expressing that something is done or exists to a satisfactory extent.
The most common and versatile adverb meaning 'sufficiently' or 'enough'. It can modify verbs and adjectives. Often used in both spoken and written Japanese.
この部屋は十分に広いです。
This room is sufficiently spacious.
He explained sufficiently.
An alternative kanji spelling of 十分に, with the same meaning and usage. Slightly more common in formal writing.
準備は充分に整っている。
Preparations are sufficiently in place.
Verb meaning 'to be sufficient' or 'to be enough'. Used to state that a quantity or degree meets the requirement. Often used in the negative form 足りない (not enough).
この量で足りますか？
Is this amount sufficient?
説明が足りなかった。
The explanation was not sufficient.
The adjectival noun form of 十分, meaning 'sufficient'. Can be used with だ/です to describe a state, or directly before a noun.
Indicating that an action has been performed to the necessary degree.
Pattern meaning 'sufficient to do ~'. Used to modify a noun that enables the action.
生きていくのに十分なお金がある。
I have enough money to live on.
Pattern meaning 'enough ~ to do ~'. Emphasizes the quantity or quality needed for the action. More literary than のに十分な.
彼にはそれを買うだけのお金がない。
He doesn't have enough money to buy that.
Expressing that an adjective applies to an adequate extent.
Adverb meaning 'considerably' or 'fairly'. Often used when 'sufficiently' implies a notable degree, not just the bare minimum.
この問題はかなり難しい。
This problem is sufficiently difficult.
Adverb meaning 'considerably' or 'quite'. Similar to かなり but slightly more formal. Implies a high degree.
十分に is an adverb that modifies verbs and adjectives, while 足りる is a verb that describes the sufficiency of a subject. Use 十分に when you want to say 'do something sufficiently', and 足りる when stating that something 'is sufficient'.
While 十分に can modify adjectives, it often sounds more natural to use かなり or 相当 when you mean 'sufficiently' in the sense of 'quite' or 'fairly'. 十分に広い is correct but may sound like 'just barely spacious enough', whereas かなり広い means 'quite spacious'.
彼は相当疲れているようだ。
He seems sufficiently tired.