Explanation of relative clauses and optional words.

 

1. The sentence:

The man writing on the board is my professor. ✅

• “writing on the board” is called a reduced relative clause.
• It’s a shorter way of saying “who is writing on the board”.

So this sentence is the same as:

The man who is writing on the board is my professor. ✅

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2. Why we can leave out “who is”

In English, when you have:

• subject + who is + verb-ing

You can drop “who is” and just keep verb-ing.

• The woman who is standing there is my aunt. → The woman standing there is my aunt.
• The people who are talking are my friends. → The people talking are my friends.

✅ Works when the relative clause uses “be” + -ing

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3. When you can’t drop “who is”

• If the clause is more complex, or the verb isn’t just be + -ing, you need who/that + verb.

Example:

• ❌ The man going to the store is my professor. → sounds okay if casual, but technically: The man who is going to the store is my professor.
• ❌ The man writes on the board is my professor. → wrong, because “writes” is present simple, not “be + -ing”

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4. Quick comparison

Full form	Reduced form
The man who is writing on the board is my professor.	The man writing on the board is my professor.
The woman who is standing by the door is my teacher.	The woman standing by the door is my teacher.

✅ Both mean the same thing, but the reduced form is shorter, smoother, more natural.

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💡 Memory trick:

• If it’s who/that + is/are + verb-ing, you can usually drop who/that + is/are and just use verb-ing.
• Sounds natural and fluent in English.