A simple sentence is an independent clause made up of a subject and a predicate expressing only one complete thought.

New York City is the largest city in the U.S. and an important seaport.

Compound sentences are made of two closely related independent clauses joined by a comma and a coordinating conjunction such as for, and, nor, but, or, yet, so (also known as “fanboys”) or by a semicolon (;).

His strategy must have worked, for the loan was granted.

A complex sentence is a sentence made up of an independent clause and a dependent clause. A dependent clause must be joined with an independent clause to make sense. A dependent clause often begins with a subordinating conjunction such as although, because, if, as, or when.

When she opened her eyes, she saw all her family gathered around her bed in the small hospital room.

A compound-complex sentence joins three or more clauses together with subordinating and coordinating conjunctions. A compound-complex sentence includes both dependent and independent clauses.

Even though floods destroy homes, they increase the fertility of soil, for rivers deposit tiny grains of soil across low-lying farmlands.