intressant

In a sentence

• Den filmen var verkligen intressant.

  That movie was really interesting.

  Here, 'intressant' modifies the noun 'film', serving as an adjective describing its quality.

• Har du hört om den intressanta upptäckten?

  Have you heard about the interesting discovery?

  In this case, 'intressanta' is the definite form of the adjective 'intressant', due to the definite noun 'upptäckten'.

• Det skulle vara intressant att se vad som händer härnäst.

  It would be interesting to see what happens next.

  Here, 'intressant' describes the abstract idea of 'seeing what happens next', functioning as an adjective linked to an infinitive clause.