naisen de buchou ni denwashimasu.

I call the manager on the internal extension.

Breakdown of naisen de buchou ni denwashimasu.

• で: means particle
• に: indirect object particle
• 電話でんわする: to call
• 部長ぶちょう: manager

Questions & Answers about naisen de buchou ni denwashimasu.

How is 内線　で　部長　に　電話します。 pronounced?

It is read:

ないせん で ぶちょう に でんわします。

In normal Japanese writing, you would usually see it without spaces:

内線で部長に電話します。

The spaces here are just to help learners see the parts of the sentence.

What does 内線 mean exactly?

内線 means an internal phone line or extension inside a company, school, hotel, and so on.

So it does not mean a regular outside phone call. It specifically refers to calling through the organization’s internal phone system.

Why is で used after 内線?

Here, で shows the means or method used to do something.

So 内線で means:

• by extension
• using the internal line
• on the internal phone system

This is a very common use of で in Japanese: it marks the tool, method, or medium.

Examples:

• バスで行きます = I go by bus
• 日本語で話します = I speak in Japanese
• 内線で電話します = I call by extension