Used as an adverb to express certainty or a high probability; synonymous with 'sicherlich' (certainly) or 'gewiss' (surely).
example
Sie hat so viel gelernt, sie besteht die Prüfung bestimmt.
She studied so much; she'll certainly pass the exam.
Usage tips
Word family
'Bestimmt' is the past participle of the verb 'bestimmen' (to determine, to define). This origin helps explain the meanings: something is already determined, certain, or intended for a purpose.
EXAMPLE
Wir müssen noch den genauen Zeitpunkt für das Treffen bestimmen.
We still have to determine the exact time for the meeting.
Adverb vs. adjective
As an adverb (meaning: certainly), 'bestimmt' is not declined. As an adjective (meaning: specific), it stands before a noun and takes an ending.
EXAMPLE
Das wird bestimmt ein schöner Abend.
That will certainly be a nice evening.
Fixed preposition
In the meaning 'vorgesehen für' (intended for), 'bestimmt' is always used with the preposition 'für' (for) and the accusative. The structure is: something is intended for someone/something.
EXAMPLE
Diese Plätze sind für Gäste mit Behinderung bestimmt.
These seats are intended for guests with disabilities.
Compare with
antonym
bestimmt vs vielleicht
maybe
'vielleicht' and 'bestimmt' are opposites when talking about how likely something is. 'vielleicht' shows uncertainty: something is possible, but not clear. 'bestimmt', on the other hand, shows great certainty or a strong expectation. If you want to stay cautious, 'vielleicht' fits. If you are almost sure, 'bestimmt' sounds more natural.
bestimmt
Die Gruppe findet bestimmt eine Lösung für das Problem.
The group will certainly find a solution to the problem.
vielleicht
Maria kauft vielleicht noch Brot, wenn der Laden offen ist.