Sentence Structure
Depending on the number and type of clauses they contain, sentences are classified as simple, compound, complex, compound-complex.
1. Simple Sentences
A simple sentence contains only one independent clause.
Without dancing, life would not be fun.
A simple sentence can also contain compound elements (subject, verb, object).
Evil enters like a needle and spreads like an oak. (compound verb)
2. Compound sentences
A compound sentence consists of two or more independent clauses with no subordinate clauses. They are joined with a comma and a coordinating conjunction (and, but, or, nor, so, for, yet) or with a semicolon.
He wanted to join the group, but the other members wouldn’t let him.
Most singers gain fame through hard work and dedication; Evita, however, found another means.
3. Complex sentences
A complex sentence is composed of one independent clause with one or more subordinate clauses.
The fur that warms a monarch once warmed a bear.
Home is the place where you slip in the tub and break your neck.
Talent is what you possess.
Dig a well before you are thirsty.
Whoever gossips to you will gossip about you.
Juan can run faster than I can bicycle.
When he adopts a creed, a scientist commits suicide.
The receptionist knows [that] you are here.
Subordinating Adverbs
after before rather than though where although even though since unless whether as as if if how so that until while than when why because in order that that because although Relative Pronouns
that who whom whose which
Other words introducing subordinate clauses whoever whomever whatever whichever whenever wherever
The above is true in both Spanish and English (Hacker, 2009, 768-770).
Run-On Sentences
Run-on sentences are a serious problem because they indicate that the writer does not understand basic sentence structure either in Spanish or English.