There are as many clauses in a sentence as there are finite verbs. A finite verb has a subject. Infinitives, participles and gerunds are not finite verbs.

For and because

For is a coordinate conjunction. It introduces a coordinate clause. Because is a subordinate conjunction. It introduces a subordinate clause.

We will not go out, for it is raining.
We will not go out because it is raining.

Here the first sentence has two coordinate clauses: we will not go out and for it is raining. The second sentence has one coordinate clause (We will not go out) and one subordinate clause (because it is raining).

Whether

Whether introduces a noun clause when it implies an indirect question.

I want to know whether he is coming. (Here the subordinate clause ‘whether he is coming’ is a noun clause acting as the object of the verb know.)

Whether introduces an adverb clause of condition when it indicates a condition and is followed by or.

You must take this medicine whether you like it or not.

Indirect questions

Indirect questions  introduced by if or whether are noun clauses.

He asked me whether I could help him. (Whether I could help him – noun clause)

After the conjunctions when, unless, if, till, whether…or, while and though, the verb to be is often understood. When analyzing sentences containing any one of the above conjunctions, first supply the omitted words.

I broke my leg, while climbing up the ladder. (= I broke my leg, while I was climbing up the ladder.)

The same word may introduce clauses of different kinds. The nature of each clause should be found out from the purpose it serves in the sentence.