Linking Clauses: όταν, αν, επειδή, ενώ, ότι

A subordinating conjunction joins a dependent clause to the main sentence:

• όταν (when): Θα φάμε όταν έρθει ο Νίκος. (We'll eat when Nikos comes.)
• αν (if): Αν έχεις χρόνο, έλα. (If you have time, come.)
• επειδή (because; also γιατί, αφού)
• ενώ (although, while; also αν και)
• ότι (that; also πως) after verbs such as νομίζω, ξέρω, λέω
• τόσο... ώστε (so... that; also που)
• πριν (before) and μέχρι να (until)

For a future event, όταν and αν take the verb form used after να, never θα: όταν τελειώσω (when I finish). πριν and μέχρι να always take this form, even about the past: Έφυγε πριν φάμε. (He left before we ate.) For past facts use the normal past tense: όταν ήμουν φοιτητής (when I was a student). For imagined situations αν takes a past form: αν ήμουν εσύ (if I were you).