Looking up...
by oneself; without anyone else present
Er ging allein nach Hause.
He went home alone.
Kann ich das allein machen?
Can I do this alone?
Can also imply independence or solitude.
only; solely
Das ist allein deine Entscheidung.
That is solely your decision.
Allein durch harte Arbeit wird man erfolgreich.
Only through hard work will you be successful.
Used to emphasize exclusivity or uniqueness.
'Allein' is often used to describe physical solitude or exclusivity in decisions.
While 'allein' can function as both, it is most commonly used as an adverb to describe actions done alone.
From Middle High German 'allein', from Old High German 'allane', meaning 'alone'. Related to the word 'all' (all alone).
Can be used both as an adjective and an adverb. Often emphasizes solitude or exclusivity.