Learn Farsi: تابستون او روی ایوون یک فنجون آب سرد می‌خوره. - In summer, he drinks a cup of cold water on the porch.

In this sentence, تابستون (summer), ایوون (porch), and فنجون (cup) all show the colloquial Tehrani sound change where the ā sound shifts to u before an n (ن). In formal written Farsi, these are تابستان, ایوان, and فنجان.

Why doesn't آب (water) change to ub?

The shift from ā to u in conversational Tehrani Persian only happens when the ā comes right before a nasal consonant: n (ن) or m (م). Since آب ends in a b (ب), the vowel doesn't change.

Is there an ezafe linking فنجون (cup) and آب (water)?

Usually, when using a container or measurement word like فنجون right before the noun it measures, you drop the ezafe in spoken Farsi. So you just say یک فنجون آب (a cup of water) without a linking vowel. However, آب and سرد are linked by an ezafe because سرد is an adjective describing the water.

Why is the verb می‌خوره instead of می‌خورد?

Since the sentence uses conversational pronunciation for the nouns, it does the same for the verb. In colloquial spoken Persian, the third-person singular ending (as in ) softens to an sound, dropping the final (د).