When it comes to complex sentences, clauses are divided into two groups: ‘Independent Clauses’ and ‘Dependent Clauses’. I find these terms a little misleading.
First of all, I get that the terms refer strictly to the structure of the sentence: an independent clause can stand on its own and be grammatically correct. But when it comes to meaning, it’s sometimes a different story. Adverbial Clauses and Relative Clauses (which are two types of dependent clauses) can be essential, which means that the so-called ‘independent’ clause does not make sense without the dependent clause. In these cases, an ‘independent’ clause is in fact dependent upon the dependent clause in order to complete its thought.
Content Clauses go a step further. Not only are they essential, but they are almost always the focus of the sentence. In fact, the ‘independent’ clauses for such sentences are there just to support and point to the Content Clause (which is a type of dependent clause).
In summary, the ‘independent’ clause is grammatically independent, but in terms of content it may or may not depend on another clause.
I like to think of these instead as ‘host’ clauses and ‘guest’ clauses. The ‘host’ (independent) clause provides the structural framework – and often the context as well – that the ‘guest’ (dependent) clause resides within. This doesn’t add to the confusion of which clause relies on the other, or which is more important.
Another thing that bothers me is that non-interrogative Content Clauses and Adverbial Clauses (again, these are dependent clauses) can in fact stand on their own grammatically if you don’t include the linking word. This is what we do for compound sentences; we consider coordinating conjunctions as separate from any of the clauses in their sentences. Yet subordinating clauses must be included as a part of a clause. It seems a bit like a double-standard, doesn’t it?
Granted, there are other factors involved, and I get that you have to draw distinctions somewhere. And you have to label things. When you categorize something as complex as language, you won’t be able to put everything in neat little boxes.
I don’t have a solution to this issue, by the way. Nor does it necessarily need to be fixed. But I think it is worth taking a closer look at what terms we use.