Learn Farsi: این نشونی برای یک دکون هندونه‌ست.

Yes! In spoken Tehrani Farsi, the 'ā' sound frequently changes to 'u' before the letters 'n' or 'm'. In this sentence, we see three perfect examples: نشانی (address) becomes نشونی, دکان (shop) becomes دکون, and هندوانه (watermelon) becomes هندونه.

In the shift from هندوانه to هندونه, what happened to the 'v' sound?

When the 'ā' shifts to 'u' before the 'n', the surrounding letters often simplify to make the word easier to say quickly. The combination 'vāne' in هندوانه shrinks down to just 'une', completely dropping the 'v' sound. This is very common in everyday speech for this specific word.

How are the words for 'shop' and 'watermelon' connected here? Is there an invisible Ezafe?

Exactly. You pronounce it as 'dokun-e hendune'. To say 'a watermelon shop' in Farsi, you use the Ezafe vowel 'e' to link the noun for shop (دکون) to its descriptor (هندونه). Because دکون ends in a consonant, this 'e' sound is spoken but not written in the Persian script.

What is the attached ‌ست at the very end of the sentence?

It is a shortened form of است (is). Because the word هندونه ends in a silent 'he' (acting as a vowel), saying the full word است right after it feels clunky in speech. Instead, the 'a' is dropped and the rest of the word is attached, creating هندونه‌ست (hendune-st).