Which is the main verb in this simple sentence?

Question

This sentence will automatically tell you that it is written in English Language.

I supposed to use it as an example in my answer, but after much considerations, I became confused.

I eliminated will because it is a modal verb. I also eliminated tell because I thought that it was not referring to this sentence which is the subject and proclaimed written as the main verb.

But then, I also thought that tell should also be able to be a main verb since it tells that it is written in English language. In other word, tells will have the biggest effect.

Answer 1

A basic sentence consists of one subject and one verb, but English sentences can be composed of multiple clauses, each which have their own subject and verb.

In your example there are two clauses junctioned by that, which is a common word for this purpose and is often optional and left out:

This sentence will automatically tell you - that - > it is written in English Language.

So there are two verbs - tell and is. Will is an auxillary of tell and written is probably technically something like a complement or "object" of is.

Note: The past participle version of a verb will never be the real verb in a sentence or clause, it always requires a form of to be or to have in front of it.

So which is the "main" verb though?

The phrase that it is written in English Language is functioning as an "object" or complement of tell - it's answering the question "what is told?" Not the other way around. Because of this, that clause is not the main clause in the sentence, so the main verb of the entire sentence is tell.