Learn Polish: Odkręć tę śrubkę i sprawdź, co tam jest. - Unscrew this screw and check what is there.

The base verb is kręcić, which means to turn, twist, or spin. When you add the prefix od-, it acts like the English prefix "un-", indicating the reversal of an action or state. Since turning a screw inward fastens it, odkręcić means to unscrew or detach it by turning.

Why is the imperative form odkręć and not odkręcaj?

Odkręć is the perfective imperative, used here because you want the person to complete the specific, one-time action of unscrewing this one screw. Odkręcaj is the imperfective imperative (from the verb odkręcać), which would be used if you were telling someone to start unscrewing things in general, or if you were urging them to keep doing it.

I often hear Polish people say tą śrubkę instead of tę śrubkę. Are both correct?

Grammatically, tę is the strictly correct accusative singular form of ta (this), matching the accusative noun śrubkę. However, in everyday spoken Polish, native speakers frequently use tą in the accusative case to match the ending of the instrumental case. At a B2 level, it is best to write tę in formal contexts, but expect to hear tą śrubkę in casual speech.

Is śrubkę a diminutive?