wǒ zài děng diànhuà.

Mandarin usually does not use a separate verb like am / is / are before an action verb.

In English, you say I am waiting.
In Mandarin, you normally say 我在等.

Here, 在 helps show that the action is in progress, so 我在等电话 corresponds to I am waiting for a phone call.

So:

• 我 = I
• 在等 = am waiting / be in the middle of waiting
• 电话 = phone call / telephone

In this sentence, 在 is marking an ongoing action. It works a bit like the English -ing idea.

So:

• 我在等电话 = I am waiting for a call

This is different from the other very common use of 在, where it means at / in / on as a location word.

For example:

• 我在家 = I am at home

So 在 can have different jobs depending on the sentence.
Here, it is not about location. It is showing that 等 is happening right now.

Because 等 in Chinese can directly take its object.

In English, you say:

• wait for a phone call

In Mandarin, you simply say:

• 等电话

So 等 already covers the idea of wait for.

A few examples:

• 等人 = wait for someone
• 等车 = wait for a bus / vehicle
• 等电话 = wait for a phone call

This is very normal Chinese grammar.

It can mean either one in different contexts, but in this sentence it usually means phone call.

So 我在等电话 is most naturally understood as:

• I’m waiting for a call
• I’m expecting a phone call

If you wanted to clearly say you were physically waiting by the telephone, you would usually say something more specific, such as:

• 我在电话旁边等
• 我守着电话

So in this sentence, 电话 is most likely understood as a call, not the physical device.

Mandarin often allows a noun to appear without a measure word or number when the meaning is general or understood from context.

So:

• 我在等电话 = I’m waiting for a call / waiting for phone calls

This sounds natural.

If you say:

• 我在等一个电话

that usually sounds more like:

• I’m waiting for a particular call
• I’m waiting for one call

So both are possible, but they are slightly different in feel:

• 等电话 = general, natural, common
• 等一个电话 = emphasizes one specific call

Yes, you can.

• 我等电话 is grammatical
• 我在等电话 is also grammatical

The difference is that 在 makes the action sound more clearly in progress right now.

Compare:

• 我等电话 = I wait for calls / I’m waiting for a call / I will wait for a call
  
  • more dependent on context
• 我在等电话 = I am waiting for a call right now
  
  • clearer ongoing-action feeling

In everyday conversation, if you want to stress what you are doing at the moment, 在 is very common.

Yes. The basic pattern here is:

• subject + 在 + verb + object

So:

• 我 = subject
• 在 = ongoing-action marker
• 等 = verb
• 电话 = object

This is a very common structure.

For example:

• 我在看书 = I am reading a book
• 他在吃饭 = He is eating
• 我们在聊天 = We are chatting

So 我在等电话 follows a very standard pattern.

Not usually, at least not by itself.

Most people will understand 我在等电话 as:

• I’m waiting for a phone call
• I’m expecting a call

If you really mean by the phone, you would usually need extra words to show location, such as:

• 我在电话旁边等
• 我在电话边上等

Without those location words, the sentence is normally about waiting for a call, not standing next to a phone.

Yes, this is natural.

A native speaker might also say slightly fuller versions depending on tone and context, for example:

• 我在等电话呢。
  This sounds a bit more conversational and ongoing.

• 我在等一个电话。
  This emphasizes one expected call.

• 我在等他的电话。
  I’m waiting for his call.

So the original sentence is fine and natural, especially as a simple example sentence.

You can put extra words before 电话.

Examples:

• 我在等他的电话。 = I’m waiting for his call.
• 我在等妈妈的电话。 = I’m waiting for Mom’s call.
• 我在等银行的电话。 = I’m waiting for the bank’s call.
• 我在等一个重要的电话。 = I’m waiting for an important call.

So 电话 behaves like a normal noun here, and you can modify it as needed.