primećivati

1. to notice
   Sve češće primećujem sede vlasi. — I'm noticing grey hairs more and more often.
   Da li primećuješ neku razliku? — Do you notice any difference?
2. to remark; to observe
   Kritičari primećuju da je film predugačak. — Critics remark that the film is too long.

The perfective is "primetiti"; "primećivati" usually describes repeated or ongoing noticing.