Learn Italian: Spero che tu dia un'anima al personaggio che interpreti. - I hope you give a soul to the character you play.

The phrase spero che (I hope that) expresses a wish, which triggers the subjunctive mood. dia is the present subjunctive form of the irregular verb dare (to give). If this were just a stated fact, it would be the normal present tense dai.

Since dia is irregular, do all the singular forms of dare share this exact same word in the subjunctive?

Yes! In the present subjunctive, the io, tu, and lui/lei forms of dare are all exactly the same: dia. Many high-frequency irregular verbs follow this pattern in the subjunctive, where the three singular forms match perfectly.

If the singular forms are all the same, is that why tu is used instead of just saying che dia?

Exactly. In the normal present tense, you can usually drop the pronoun because the unique verb ending makes it obvious who is acting. Because dia could mean I, you, he, she, or it, we include tu here to make it crystal clear that you are the one giving the soul.

Why is interpreti in the normal present tense when the sentence starts with spero che?