Question

The room is six metre long. (Noun form of long)

Answer 1

Noun form of long - $\rm\purple{ Length}$

So , when we use the noun form of long that is length(abstract noun) in the sentence ; the structure of the sentence will modify a bit :

1. The article the will be precede the noun.
2. We would use of after the noun.
3. We would then put up the remaining part of the sentence as it is.

We get :

$\rm\purple{ The\: length\: of \:the\: room\: is\: six \:metres.}$

Answer 2

• The room is six metre long.

→ The length of the room is six metre.