من با تلفن به مادرم زنگ میزنم، چون او امروز بیمار است.

زنگ زدن is a very common compound verb in Persian. Literally, it originally has the idea of ringing, but in modern usage it often means to call / to phone.

So in this sentence:

• زنگ = ring, bell, call
• می‌زنم = I do / I strike / I make

Together, زنگ می‌زنم means I call.

This is normal in Persian: many verbs are built from a noun + a light verb such as زدن, کردن, شدن, etc.

With the verb زنگ زدن, the person you call is usually marked with به.

So:

• به مادرم زنگ می‌زنم = I call my mother

A native English speaker may expect something more like I call my mother with no extra word, but Persian treats it more like I ring to my mother.

So with this verb, به is the normal pattern.

The -م at the end is a possessive ending meaning my.

So:

• مادر = mother
• مادرم = my mother

This is very common in Persian:

• دوستَم = my friend
• کتابَم = my book
• برادرَم = my brother

You can also say مادر من, but مادرم is shorter and very natural.

Usually, زنگ زدن already makes it clear that you mean to call / to phone. So in many situations, با تلفن is not necessary.

You could simply say:

• به مادرم زنگ می‌زنم

and that would sound completely natural.

با تلفن adds the idea of by phone / on the phone, but it can feel a little explicit or slightly redundant unless you are contrasting it with some other method.

چون means because.

It introduces the reason:

• چون او امروز بیمار است = because she/he is sick today

This is a very common everyday word. It works much like English because.

Other possibilities exist, such as:

• زیرا = because, since, more formal
• برای اینکه = because, so that, depending on context

But چون is simple and very common.

Yes, it could.

• او is the more standard, written, or formal form for he / she
• اون is the more colloquial spoken form

So:

• چون او امروز بیمار است sounds more standard/written
• چون اون امروز بیماره sounds more conversational

Both are correct in the right context.

Persian usually puts the verb at the end of the clause.

So:

• او امروز بیمار است
• literally: she/he today sick is

That is normal Persian word order.

Also, است is the formal/full form of is. In everyday speech, it is often shortened:

• بیمار است → بیماره

So a spoken version might be:

• اون امروز بیماره

Often, yes.

Persian is a pro-drop language, which means subject pronouns are often omitted when the verb already makes the subject clear.

For example:

• زنگ می‌زنم already shows I call
• بیمار است already shows he/she is sick

So this sentence could often be shortened to:

• به مادرم زنگ می‌زنم، چون امروز بیمار است.

Pronouns like من and او are often kept for:

• emphasis
• contrast
• clarity

The standard spelling is می‌زنم with a half-space after می.

So the most careful written form is:

• می‌زنم

But many people type:

• میزنم

especially in casual texting or informal writing.

Both are understood, but if you are learning standard written Persian, it is better to write می‌زنم.

There is no را because مادرم is not being treated as a normal direct object here.

With زنگ زدن, the person you call usually comes with به:

• به مادرم زنگ می‌زنم

So را is not used.

A learner might expect something like a direct object marker, but this verb simply works differently.

Yes, بیمار is a correct and common word meaning sick / ill. It can sound a little more neutral or slightly more formal than some everyday alternatives.

In casual speech, many people also use:

• مریض

So you may hear:

• او امروز بیمار است more standard/written
• اون امروز مریضه more conversational

Both are common, though style and region can affect preference.

A more conversational version might be:

• به مادرم زنگ می‌زنم، چون اون امروز بیماره.

Or even:

• به مادرم زنگ می‌زنم، چون امروز بیماره.

Compared with the original sentence:

• the pronoun من is dropped
• او becomes اون
• است becomes ه
• با تلفن is omitted because زنگ زدن already implies calling

So the original sentence is correct, but it sounds a bit more careful or written than everyday speech.