πριν

In a sentence

• Πήγαινα στη δουλειά πριν αρχίσει να βρέχει.

  I was going to work before it started raining.

  Here, 'πριν' is used as a conjunction to indicate a prior event.

• Θέλω να ξεκουραστώ πριν το δείπνο.

  I want to rest before dinner.

  In this instance, 'πριν' serves as a preposition followed by a noun to denote an earlier time compared to an event.

• Δεν είχα ξαναδει την ταινία πριν.

  I had not seen the movie before.

  'Πριν' is used as an adverb here, indicating a time prior to the moment referred to.