おそらく: 'Probably' / 'Most Likely'
How sure "probably" actually is
おそらく (恐らく) is an adverb of likelihood: you set it near the front of a sentence to say something is probably or most likely so. It is a confident guess — not a fact you can vouch for, but a strong lean. That confidence level is the whole point of the word, and it's what separates it from a mere "maybe."
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.
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.
The adverb that needs だろう to land
Because おそらく carries no conjugation of its own, the grammar work happens at the end of the sentence. おそらく raises a conjecture flag, and a conjecture ending — だろう / でしょう / と思う lowers it. Leave that ending off and the sentence feels truncated: おそらく彼は来ない sounds unfinished next to おそらく彼は来ないだろう.
Where the adverb sits is flexible — おそらく彼は来ない and 彼はおそらく来ない are equally fine. What is not flexible is the ending; that pairing is the part learners drop.
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.
Where it sits next to たぶん and もしかしたら
おそらく, たぶん, and もしかしたら all translate as "maybe / probably," but they split on confidence and register:
- おそらく — probably / most likely. Fairly high confidence, and slightly formal or written; you'll meet it in news, essays, and careful speech.
- たぶん — probably. Roughly the same confidence as おそらく, but casual and everyday — the one you reach for in conversation. (たぶん明日は晴れるよ。) So the gap between them is tone, not certainty; with friends, おそらく行くよ sounds stiff where たぶん行くよ is natural.
- もしかしたら — maybe / possibly. A lower probability that flags a real but uncertain chance, and it 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。) If you mean a slim possibility rather than a confident lean, this is the one to use.
The one clash to watch: guesses vs guarantees
The subtle trap is mixing おそらく with certainty words. Because it expresses a guess, it can't share a clause with 絶対 ("definitely") or 必ず ("without fail") — a confident lean and a guarantee pull against each other. Keep おそらく for the conjecture, and let だろう / でしょう / と思う finish the thought.
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.
The short version
- 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.
- Don't pair it with 絶対 or 必ず — a guess can't carry a guarantee.
Practice it
Choose the natural sentence using おそらく with the right ending.
＿＿＿に入れるのに最もよいものを選びなさい。
＿＿＿、人間の持って生まれた感情の中で、虚栄心ほど抑えにくいものはないだろう。
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.
Where おそらく fits
Shaky on this? Get these solid first
- 〜ようだ · N4 — 〜ようだ states a conjecture from your own evidence ('it seems') and, as 〜ように / 〜ような, draws comparisons ('like'). Learn the attachment rules and how it differs from みたい and らしい.
Don't confuse it with
- 〜かもしれない · N4 — かもしれない means 'might' or 'maybe' — it shows you're unsure. Learn how it attaches to plain verbs, adjectives, and nouns, plus the casual かも and how it ranks against でしょう and はず.
Once this clicks, go on to
- 〜でしょう / 〜だろう · N5 — でしょう means 'probably' and, with a rising tone, 'right?'. Learn how it attaches to verbs, adjectives, and nouns, its casual form だろう, and why forecasts love it.
More N3 grammar to explore
Keep going with related patterns at the same level:
- 〜っぱなし — 〜っぱなし attaches to a verb stem to mean leaving something in a state without undoing it (often carelessly) — or something that keeps happening nonstop. Forms and nuance inside.
- 〜っぽい — 〜っぽい adds a '-ish/-like' nuance: 子供っぽい (childish), 忘れっぽい (forgetful), 安っぽい (looks cheap). Learn the noun and verb-stem patterns, the い-adjective conjugation, and the critical tone.
- 〜最中に — 〜最中に marks the very thick of an ongoing action — often when it's interrupted: 食事の最中に電話が鳴った. Learn the noun+の and 〜ている patterns, plus how it differs from 〜ているところ and 〜間に.
- 確かに — 確かに (たしかに) means 'certainly / indeed.' Learn its two uses — affirming a point and the concessive 確かに〜が ('it's true that X, but…') — plus how it differs from 確か.
- たとえば — たとえば (例えば) means 'for example.' Learn how it introduces a concrete example of a general statement, the たとえば〜など pattern, and why it's not the same as たとえ (even if).
- 〜てこそ — 〜てこそ marks an action as the indispensable basis for a good result: 努力してこそ成功する ('only by trying hard do you succeed'). Learn the formation, nuance, and pitfalls.