1.
no longer; not anymore (with negative)
Used with negative expressions to indicate that something is no longer the case. Implies a change from a previous state.
2.
already; by now; at this point
Indicates that a situation has reached a certain point. Often used to emphasize that something has become inevitable or has progressed beyond a certain stage.
Usage
最早 marks a line already crossed. With a negative it says something is no longer so; with a plain statement it says the situation has already reached a point there is no arguing with. Either way it looks back at a change that has finished, which is what separates it from もう — the everyday word that covers the same ground without the note of finality.
Common patterns
- 最早〜ない: no longer ~
- 最早元には戻らない: will never go back to how it was
- 最早これまでだ: this is the end of it
- 最早疑う余地はない: there is no longer room for doubt
Writing
Usually written in kana as もはや. The kanji spelling 最早 is a jukujikun — the reading does not follow from the individual characters — and belongs to formal or literary writing.
Register
Formal and somewhat literary. In speech もう does the same work: 最早〜ない (written) = もう〜ない (spoken). 最早 also turns up in commentary and headlines for rhetorical weight, as in これは最早災害レベルだ.