Learn Turkish: Nehirler yüksek dağlarda başlar. - Rivers start in high mountains.

The verb root is başla- (to start). In the Aorist (simple present) tense, whenever a verb root ends in a vowel, you simply add -r. We use this tense here because it describes a general, timeless fact about nature.

Why isn't the verb plural (başlarlar) since the subject is plural (Nehirler)?

In Turkish, when a plural subject is not human (like objects, animals, or in this case, rivers), the verb usually stays in the singular form. Nehirler başlar is the natural and grammatically correct way to say it.

Is the verb root başla- related to the word baş?

Yes! The noun baş means head or beginning. Adding the suffix -la turns it into an action, giving us the verb root başla- which means to start or to begin.

How are the suffixes ordered in dağlarda?

Suffixes stack in a specific order. First comes the plural suffix -lar to make dağ (mountain) into dağlar (mountains). Then comes the location suffix -da (in/on/at) to make dağlarda (in the mountains).