おそらく: 'Probably' / 'Most Likely'
What it means
おそらく (恐らく) is an adverb you place near the front of a sentence to say that something is probably or most likely the case. It expresses a confident guess — not certainty, but a strong lean.
The key habit to build: おそらく looks forward to a conjecture ending. It sets up the guess, and a word like だろう / でしょう / と思う finishes it. Think of them as a matched pair.
おそらく彼は来ないだろう。
おそらく かれは こない だろう。
He most likely won't come.
おそらく…だろう — the classic pairing.
おそらく明日には届くでしょう。
おそらく あしたには とどく でしょう。
It will probably arrive by tomorrow.
でしょう gives a politer conjecture ending.
ヤッタンはおそらくもう寝ていると思う。
ヤッタンは おそらく もう ねていると おもう。
Yattan is probably already asleep, I think.
How to form it
おそらく is an adverb, so there's nothing to conjugate. You just drop it in — typically right after the topic — and make sure the sentence ends in a conjecture form.
| Sentence part | Pattern | Example |
|---|---|---|
| Adverb | おそらく | おそらく |
| Clause | (plain statement) | 雨が降る |
| Conjecture ending | だろう / でしょう / と思う | 雨が降るだろう |
| Full | おそらく + clause + ending | おそらく雨が降るだろう |
Position is flexible: おそらく彼は来ない and 彼はおそらく来ない are both fine. What matters is the ending, not where the adverb sits.
More examples
この問題はおそらく試験に出るでしょう。
この もんだいは おそらく しけんに でる でしょう。
This problem will most likely appear on the exam.
モチはおそらく道に迷ったのだろう。
モチは おそらく みちに まよったの だろう。
Mochi has probably gotten lost.
のだろう adds an explanatory feel — 'it must be that…'.
先生はおそらくもう帰られたと思います。
せんせいは おそらく もう かえられたと おもいます。
The teacher has probably already gone home, I think.
と思います keeps the polite, formal tone おそらく prefers.
おそらく弟が食べたのだろう。
おそらく おとうとが たべたの だろう。
My little brother probably ate it.
おそらく vs たぶん vs もしかしたら
These three all translate as "maybe / probably," but they differ in confidence and register:
- おそらく — probably / most likely. Fairly high confidence. Slightly formal or written; you'll see it in news, essays, and careful speech.
- たぶん — probably. About the same confidence as おそらく, but casual and everyday. This is the one you reach for in normal conversation. (たぶん明日は晴れるよ。)
- もしかしたら — maybe / possibly. Lower probability — it flags a real but uncertain chance, and often pairs with 〜かもしれない. (もしかしたら雨が降るかもしれない。)
So おそらく and たぶん sit at a similar confidence level; the difference is tone. もしかしたら steps down to a weaker "it might just be."
Common mistakes
- Ending with a flat assertion. おそらく needs a conjecture, not a plain statement: おそらく彼は来ないだろう (✓), not ✗おそらく彼は来ない (sounds unfinished/odd). Pair it with だろう, でしょう, or と思う.
- Using it in casual chat. In a relaxed conversation, おそらく can sound stiff. Prefer たぶん with friends: たぶん行くよ, not おそらく行くよ.
- Treating it like もしかしたら. おそらく is a confident guess. If you mean a slim possibility, use もしかしたら〜かもしれない instead.
- Pairing it with certainty words. Don't combine おそらく with 絶対 ("definitely") or 必ず ("without fail") — it expresses a guess, so a certainty marker clashes with it.
Quick recap
- おそらく = "probably / most likely" — a confident guess.
- It pairs with a conjecture ending: だろう / でしょう / と思う.
- Register is slightly formal/written; the casual equivalent is たぶん.
- For a weaker "maybe," use もしかしたら〜かもしれない.
Your turn
Choose the natural sentence using おそらく with the right ending.
Start the 5-question drill →Frequently asked questions
What's the difference between おそらく and たぶん?
They express similar confidence ('probably'), but おそらく is slightly formal or written, while たぶん is casual and everyday. In conversation, prefer たぶん; in writing or careful speech, おそらく fits.
Does おそらく have to end in だろう or でしょう?
It strongly prefers a conjecture ending — だろう, でしょう, or と思う. Ending with a flat assertion (おそらく彼は来ない) sounds unfinished, so add a guess form.
How confident is おそらく?
Fairly confident — a strong lean, not certainty. It's higher than もしかしたら ('maybe, possibly') and roughly the same as たぶん, just more formal in tone.
Can I use おそらく with かもしれない?
It's unusual. おそらく signals a confident guess, while かもしれない flags a weaker possibility, so they pull in different directions. Pair かもしれない with もしかしたら instead.