おそらく (osoraku): Probably or most likely
おそらく (osoraku)
Meaning
perhaps; likely; probably
Formation and usage
おそらく + clause（だろう）
Notation: N = noun; V dictionary = dictionary-form verb; V stem = the stem before ます; plain clause = plain-form clause; negative stem = the form before ない. Follow the attachment shown above.
Explanation
A reasonably grounded but uncertain prediction, often paired with だろう or と思う.
Examples
おそらく、会議は予定どおり始まるだろう。
Most likely, the meeting will start as scheduled.
おそらく、試験は予定どおり始まるだろう。
Most likely, the exam will start as scheduled.
おそらく、研修は予定どおり始まるだろう。
Most likely, the training session will start as scheduled.
おそらく、発表会は予定どおり始まるだろう。
Most likely, the presentation event will start as scheduled.
おそらく、面接は予定どおり始まるだろう。
Most likely, the interview will start as scheduled.
How related patterns differ
に違いない expresses a confident inference; に決まっている conveys strong personal certainty. どうやら suggests a judgment from signs, while おそらく expresses likelihood. まさか signals disbelief or surprise and does not make every sentence negative by itself.