Sentences are generally classified into 4 different categories. They are as follows.
1. Simple sentences: These types of sentences contain only one main clause.
E.g., The document recommended corrections.
2. Compound sentences: These types of sentences contain two or more main clauses connected with conjunctions.
E.g., The document recommended corrections, and established time limit.
3. Complex sentences: These types of sentences contain one main clause and one or more subordinate clauses (clauses that would be fragments if disconnected from the main clause).
E.g.,
a) The document, which will form the basis of our decision, recommended corrections.
b) The document recommended corrections because these are the only way to solve the problem.
4. Compound-complex sentences: These types of sentences contain two or more main clauses and one or more subordinate clauses.
E.g., The document recommended corrections and established time limit, because that is the only way to solve the problem.
In this way, it can be noted that the different types of sentences are more about the prioritisation of information than about length. In fact, a simple sentence can be much longer than a complex one.
E.g.,
Complex sentence: The key that opens the door is small.
Simple sentence: Early in the morning, in the dusky summer sunlight, the tall, blond man and his dog came out of the building from the back door, slowly and surreptitiously.