Learn Farsi: گنجایش این کوله‌پشتی خیلی محدود است. - The capacity of this backpack is very limited.

It comes from the verb gonjidan, which means "to fit" or "to be contained." The suffix -esh is used to turn the verb root into a noun, so gonjâyesh literally means "the ability to fit" or "capacity."

How does the word mahdud (limited) relate to the current lesson's phrase tâ hadd-e emkân?

They share the same Arabic root. Hadd means "limit" or "boundary." Mahdud means "limited" (having boundaries), while the lesson's target phrase tâ hadd-e emkân literally translates to "up to the limit of possibility."

How is the compound word kule-poshti (backpack) constructed?

It is made up of kule (a load or bundle), posht (back), and the suffix -i which turns it into a related noun. Together, they form a "back-load" or backpack.

If I wanted to say "Fill this backpack to maximum capacity," how could I incorporate the current lesson's target grammar?

You can use tâ hadd-e emkân (as much as possible) to express maximum capacity here. For example: tâ hadd-e emkân in kule-poshti râ por kon (Fill this backpack as much as possible).