Learn Turkish: Daha hızlı koşsan trene yetişirsin. - If you ran faster, you would catch the train.

This sentence uses the hypothetical conditional. By attaching the conditional suffix -sa directly to the verb stem (koş-) without a tense marker, we get koşsan ("if you ran"). If you used the aorist tense first to make koşarsan, it would mean "if you run" (a real possibility).

How does yetişirsin translate to "you would catch"?

In the main clause of a hypothetical "if" sentence, Turkish uses the aorist tense (here, the -ir in yetişirsin) to express the idea of "would". Outside of an "if" sentence, yetişirsin usually just means "you catch" or "you will catch".

Why does tren (train) have the -e ending?

In English, you "catch the train" using a direct object. However, the Turkish verb yetişmek (to catch, to reach, or to make it on time) requires the dative case (-e or -a). You are literally saying you would "reach to the train".

Why do the "you" endings look different in koşsan and yetişirsin?