Αν ξεχάσω το πορτοφόλι μου στο σπίτι, θα ξαναγυρίσω αμέσως.

If I forget my wallet at home, I will go back immediately.

Breakdown of Αν ξεχάσω το πορτοφόλι μου στο σπίτι, θα ξαναγυρίσω αμέσως.

• το σπίτι: the home
• μου: my
• σε: at
• θα: will

Questions & Answers about Αν ξεχάσω το πορτοφόλι μου στο σπίτι, θα ξαναγυρίσω αμέσως.

Why is it αν ξεχάσω and not αν ξεχνάω or αν θα ξεχάσω?

After αν meaning if, Greek normally uses the subjunctive form for a possible future situation. That is why you get αν ξεχάσω.

• ξεχάσω = subjunctive/perfective form of ξεχνάω / ξεχνώ
• It refers to a single possible event: if I forget

Why not the others?

• αν ξεχνάω would suggest a more habitual or ongoing idea, like if I am forgetting / if I tend to forget
• αν θα ξεχάσω is not the normal structure in standard Greek for this kind of if clause

So:

• Αν ξεχάσω... = If I forget...
• This is the natural pattern for a real future possibility.

What exactly is ξεχάσω grammatically?