Questions & Answers about Der Mann wirkt heute müde.
In Der Mann wirkt heute müde., wirkt means seems / appears / comes across as.
- Der Mann ist heute müde. → The man is tired today. (a factual state)
- Der Mann wirkt heute müde. → The man seems/appears tired today. (your impression)
So wirken expresses a subjective impression rather than an objective fact. You’re commenting on how he comes across to you (his behavior, face, voice, etc.), not necessarily on what is actually true.
The infinitive is wirken.
Present tense (Präsens):
- ich wirke – I seem / I have an effect
- du wirkst – you seem
- er/sie/es wirkt – he/she/it seems
- wir wirken – we seem
- ihr wirkt – you (plural) seem
- sie/Sie wirken – they / you (formal) seem
In the sentence Der Mann wirkt heute müde., der Mann = er, so you use wirkt (3rd person singular).