Learn Farsi: این قسمت از بوم صرفاً با رنگ آبی پر می‌شود. - This part of the canvas is solely filled with blue color.

To make a compound verb passive in Farsi, you change the 'doing' auxiliary verb (کردن) to the 'becoming' auxiliary (شدن). Here, the active verb پر کردن (to fill) changes to the passive پر شدن (to be filled). It is conjugated in the present tense as پر می‌شود.

Notice the ending on صرفاً (serfan). How does this ending work in Farsi?

The اً suffix is called 'tanvin' and comes from Arabic. It acts similarly to the English suffix '-ly', turning a word into an adverb. Here it changes a base concept of 'pure' or 'exclusive' into the adverb 'solely' or 'merely'. You will see this often in intermediate and formal Farsi texts.

Why do we use the preposition با (with) here instead of از (of) to say what the canvas is filled with?

When talking about the physical material or substance used as a tool to fill a space, Farsi typically uses با (with). You will often see از used with the adjective 'full' (پر از - full of), but because we are using the passive verb 'is filled' here, با correctly marks the material doing the filling.

Does the word بوم (bum) refer to any type of canvas material?

No, بوم specifically refers to an artist's painting canvas. If you were talking about the heavy canvas fabric used for making backpacks, tents, or sails, you would use a different word like برزنت.