What is the difference between "crowd" and "crowding"? In the following sentence can we use both of them in place of each other?
By building a branch campus, some of the crowding (?=crowd) on the main campus may be resolved.
You need 'crowding'.
'Crowd' is a noun and simply means a large group of people
'Crowding' is the present participle of the verb 'to crowd' and is functioning as a noun in this sentence. Its meaning is the condition caused by a lot of people being within a comparatively small space at the same time. For example, it makes sense to say, "A large crowd in a confined space will cause crowding."