GRAMMAR
恐らく
probably
likely
Explanation
NOTE
恐らく means probably or likely — used when the speaker makes a confident guess based on reasoning or evidence.
恐らく彼は来ないだろう。
He probably won't come.
Sentence-initial 恐らく sets up a confident prediction, usually paired with だろう / でしょう / と思う at the end.
NOTE
It is more formal and written than たぶん. Use it in news, essays, and polite speech where the speaker sounds measured rather than casual.
NOTE
恐らく is almost always placed at the start of the sentence and works as an adverb, modifying the whole clause that follows.
STRUCTURE
恐らく+Sentence+だろう / でしょう / と思う
恐らく明日は雨でしょう。
Osoraku ashita wa ame deshou.
It will probably rain tomorrow.
恐らく彼女は事実を知っていると思う。
Osoraku kanojo wa jijitsu wo shitte iru to omou.
I think she likely knows the truth.
恐らくこの計画は失敗するだろう。
Osoraku kono keikaku wa shippai suru darou.
This plan will probably fail.
Practice exercises
1
その計画は恐らく困難に直面するだろう。
The plan will probably face difficulties.
Answer
恐らく
2
彼は来ないだろう。恐らく忙しいに違いない。
He probably won't come. He is probably busy.
Answer
恐らく
3
経済は恐らく回復すると考えられる。
The economy is likely to recover.
Answer
恐らく
4
彼女は恐らく忘れまい。
She will probably not forget.
Answer
恐らく
5
そのプロジェクトは恐らく成功するだろう。
The project will probably succeed.
Answer
恐らく