Learn Farsi: ریزش برگ‌ها در این فصل اتفاق می‌افتد.

ریزش (rizesh) is an action noun meaning "falling" or "spilling". It is formed by taking the present stem of the verb ریختن (rikhtan, meaning "to fall" or "to pour") — which is ریز (riz) — and adding the suffix ـِش (-esh). This suffix turns a verb stem into a noun representing the action of that verb.

Why is there an "e" sound connecting ریزش and برگ‌ها when spoken?

That is the Ezafe! When spoken, it connects the two nouns as ریزشِ برگ‌ها (rizesh-e barg-ha), which translates literally to "the falling of the leaves". Because Farsi generally doesn't write short vowels, the "e" sound isn't written out in the sentence, but it is required here to link the noun to its possessor.

What is the literal translation of the verb اتفاق می‌افتد?

The infinitive is اتفاق افتادن (ettefaq oftadan), which means "to happen" or "to occur". Literally, اتفاق means "event" or "occurrence", and افتادن means "to fall". So, the phrase literally translates to "an event falls". In this sentence, می‌افتد is in the present tense, meaning "happens".

Both ریزش and می‌افتد relate to "falling". Are their roots used differently?

Yes! ریختن (the root of ریزش) usually refers to things pouring, spilling, or scattering in large numbers, like leaves, rain, or hair falling out. افتادن (the root of می‌افتد) generally refers to a single object dropping. Here, is used figuratively in the compound verb to mean "to happen".