Si pierdo el metro, voy a llegar tarde a clase.

If I miss the underground, I’m going to arrive late to class.

Breakdown of Si pierdo el metro, voy a llegar tarde a clase.

• yo: I
• ir: to go
• a: to
• tarde: late

Questions & Answers about Si pierdo el metro, voy a llegar tarde a clase.

Why is it si pierdo and not si perderé?

Because after si for a real, possible future condition in Spanish, you normally use the present tense, not the future.

So Spanish says:

• Si pierdo el metro, voy a llegar tarde.

Literally, that is something like:

• If I miss the metro, I’m going to arrive late.

English often uses present after if too: If I miss the metro..., not If I will miss the metro...

So this structure is very normal:

• Si + present, then a future idea in the main clause.

Examples:

• Si llueve, no salgo.
• Si tengo tiempo, te llamo.
• Si pierdo el metro, llegaré tarde.

Why is pierdo in the present tense if the sentence is about the future?

In Spanish, the present tense is often used after si to talk about a future possibility.

So si pierdo el metro does not mean only if I am missing the metro right now. In this context, it means if I end up missing the metro / if I miss the metro.

This is just how Spanish expresses this kind of condition:

• Si estudio, aprobaré. = If I study, I’ll pass.
• Si llegas tarde, empezamos sin ti. = If you arrive late, we’ll start without you.

What kind of si sentence is this?