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は遅れるだろう

will probably be late

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phrase Rare #30,370
will probably be late 遅れる can mean that a person is late or that a scheduled event or transport is delayed. だろう expresses a prediction or likelihood.
JA: バスは遅れるだろう。
EN: The bus will probably be delayed.

十中八九彼は遅れるだろう。

He'll be late nine times out of ten.

列車の出発は遅れるだろう。

The train's departure will probably be delayed.

次のバスには遅れるだろうが、とにかく真夜中前には着くよ。

We’ll probably miss the next bus, but we’ll get there before midnight anyway.

天候のためレースの開始は遅れるだろう。

The race will probably be delayed due to the weather.

たぶん事故で彼の到着は遅れるだろう。

His arrival will probably be delayed because of an accident.