I need to do the work.
In this sentence, which is the main verb? Is it need or do?
I think the main verb is do and need to is a semi modal. Am I correct?
One of my friends said that need is the main verb here and to do the work is a prepositional phrase. Now I am really confused.
There's no modal or semi-modal verb here.* The main verb is "need" because it's the head of the verb phrase and "to do the work" is what some linguists call a catenative complement. "Catenative" means "chaining" and reflects the way that the verb can link recursively with other catenatives to form a chain: e.g. He needs to try to make him do the work.
*The modal need 1. requires a bare infinitival (infinitive without "to") clause as a complement: e.g. I need do the work; 2. It can invert with the subject in the interrogative clause:e.g. Need I do the work?; 3. It doesn't require do to be negated: e.g. I need not do the work. .
