What does "be of adjective or noun" means, and how to use it

[waterborne]

Hi, teacher

This time I have a question on the expression "be of adjective or noun", for example when I was of your age, what is the grammar rule for it?
Thanks a lot?

[Barb_D]

Generally, what comes after an "of" will be a noun phrase.

Usually, I'd say only "when I was your age." ("Age" is still a noun here. "Your" will come before a noun phrase as well.) To me "When I was of your age" doesn't sound natural.

He is of an age when he should know better.

[Raymott]

Hi, teacher

This time I have a question on the expression "be of adjective or noun", for example when I was of your age, what is the grammar rule for it?
Thanks a lot?

I don't know if there's a rule. It's more common (I'd say) with a noun before "of".
"When I was a young man of your age / a boy of your age ..."
"He's a man of strong character."
"She's a lady of good breeding."

It might be best to use such a 'person' noun when you use this type of construction; and when you read it or see it, just assume that "He is of ... " means "He is a person of ..."

[waterborne]

Thank you very much, Raymott