A sentence may be one of four kinds, depending upon the number and type(s) of clauses it contains.
An independent clause contains a subject, a verb, and a complete thought.
A dependent clause contains a subject and a verb, but no complete thought.
1. A SIMPLE SENTENCE has one independent clause.
Punctuation note: NO commas separate two compound elements (subject, verb, direct object, indirect object, subjective complement, etc.) in a simple sentence.
2. A COMPOUND SENTENCE has two independent clauses joined by
A. a coordinating conjunction (for, and, nor, but, or, yet, so),
B. a conjunctive adverb (e.g. however, therefore), or
C. a semicolon alone.
Punctuation patterns (to match A, B, and C above):
A. Independent clause, coordinating conjunction independent clause.
B. Independent clause; conjunctive adverb, independent clause.
C. Independent clause; independent clause.
Punctuation patterns (to match A, B, C and D above):
A. Dependent clause, independent clause
B. Independent clause dependent clause
C. Independent, nonessential dependent clause, clause.
D. Independent essential dependent clause clause.
4. A COMPOUND-COMPLEX SENTENCE has two independent clauses joined to one or more dependent clauses.
Follow the rules given above for compound and complex sentences.
A compound-complex sentence is merely a combination of the two.
CONNECTORS--COMPOUND AND COMPLEX SENTENCES
Two independent clauses may be joined by
1. Coordinating conjunctions (FANBOYS) Ic, and ic
2. Conjunctive adverbs Ic; therefore, ic.
A dependent (subordinate) clause may be introduced by
1. Subordinating conjunctions (ADVERB CLAUSE) Dc, ic. or Ic dc.
2. Relative pronouns (ADJECTIVE CLAUSE) I, dc, c. or I dc c.
3. Relative pronoun, subordinating conjunctions, or adverbs (NOUN CLAUSE)