Learn Farsi: بیا زباله‌ها را در پارک نیندازیم. - Come, let's not throw garbage in the park.

biyâ is used here as a suggestion word, much like 'let's' in English. Even though the main action is 'let's not throw' (which is 'we'), you use the singular biyâ because you are talking to one specific person. If you were suggesting this to a group of friends, you would use the plural form biyâyid.

Why doesn't the verb neyandâzim (let's not throw) have the usual be- prefix for the subjunctive?

When you make a subjunctive verb negative, the negative prefix na- (or ne-) completely replaces the be- prefix. You never use both together! Also, because the verb stem for throwing starts with a vowel (andâz), Farsi adds a 'y' sound in the middle to make it flow better, resulting in neyandâzim.

Why is the object marker râ used after zobâle-hâ (garbage)?

Even though 'garbage' feels like a general concept in English, adding the plural -hâ and râ makes it a specific direct object in Farsi. It means you are talking about specific trash (like the wrappers in your hands) or the concept of 'the trash' that belongs to you both, rather than just doing a general activity of 'garbage-throwing'.

Why is zobâle (garbage) pluralized with -hâ here?

In English, 'garbage' is a mass noun that doesn't usually take an 's'. In Farsi, it is very common to add the plural suffix -hâ to such words to talk about all the individual pieces of trash scattered around or being thrown away.