A sentence is...
Example: A man had two sons.
A single clause, as above, is sufficient for a sentence since it is finite and independent...
Having a finite independent clause is both a necessary and sufficient condition.
Example: After he had collected his share of the property, the younger son left for a distant place and there (he) wasted his money on a life of debauchery.
There are three clauses and two connecting words in this example.
2, 3, and 5 are the clauses; and 1 and 4 are the connecting words.
When two clauses are connected, they may have either of these two relationships:
The following two clauses...
Here's a test...
If with either of the two clauses, we ask any of the following questions: what, whom, which, what kind of, how, when, where, why; we do not get the other clause as an answer, because that other clause is independent.
For instance, if you ask the question:
"The younger son left for a distant place" - when/where/why/...?
you don't get the other clause as the answer.
Here too, we have two clauses...
If you use the test I mentioned above, and ask the question when with the second clause, you get the first clause as an answer along with the connecting word. That's why we always include the connecting word as part of the dependent (i.e. depending) clause.
You may have any number of clauses. You may have more than one independent clause. It does not matter.
It doesn't also matter if there are non-finite clauses or not. They are not essential.
The various types are Simple, Complex and Compound (also sometimes a fourth type, Complex-compound). They are based on the pattern of combination of independent and dependent finite clauses.
It contains a single clause. Remember it needs to be an independent finite clause. - e.g. Then he came back to his senses.
It contains a number of clauses, which depend, directly or indirectly, upon one single independent clause. - e.g. When he had spent all the money, that country experienced a severe famine.
It is a mixture of sentences. Each sentence that is part of a Compound Sentence is called a Coordinate Clause.
A coordinate clause may be a simple sentence or a complex sentence. This means...
A Compound Sentence may have any of the following mixing patterns:
e.g. I will leave this place and (I will) go back to my father.
When the Coordinate Clauses are all Simple Sentences, then the combined sentence is called simply a Compound Sentence. (In my opinion, it should be called a Simple Compound Sentence.)
For example: While the young man was still a long way off, his father saw him and (he) was moved with pity.
Some people call this type of sentence (as well as the one following) a Complex-compound Sentence because at least one of the constituents is a Complex Sentence.
e.g. Now the elder son, who was out in the fields, was coming back and as he drew near the house, he heard music and dancing.
As I implied a little earlier, I would find it more consistent to divide Compound Sentences into...
...if we have at all to divide them!
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