What is Complex Sentence?

A sentence that contains an independent clause and at least one dependent clause.

The complex sentence is one of the four basic sentence structures. The other structures are the simple sentence, the compound sentence, and the compound-complex sentence.

See also:

Examples and Observations:

· "[I]n the complex sentence John left when his sister arrived, the clause when his sister arrived is a dependent clause because it is preceded by the word when, which is a subordinating conjunction. Dependent clauses are not complete sentences; they cannot stand alone as a complete sentence. For example, *When his sister arrived cannot stand alone. Dependent clauses must be attached to independent clauses in order to form a complete sentence. In the complex sentence above, John left is the independent clause."
(Denise E. Murray and Mary Ann Christison, What English Language Teachers Need to Know. Routledge, 2011)

Martina laughed when her mother dropped a pie upside down on the floor.

"[W]hen my brother got his pants leg caught on the top of a high fence and hung upside down, weeping and muttering curses because his pants were newly torn and Mother would spank him for sure, no angel was with him."
(Gary Soto, A Summer Life. University Press of New England, 1990)

"The Scarecrow and the Tin Woodman stood up in a corner and kept quiet all night, although of course they could not sleep."
(L. Frank Baum, The Wonderful Wizard of Oz, 1990)

"Although volume upon volume is written to prove slavery a very good thing, we never hear of the man who wishes to take the good of it by being a slave himself."
(Abraham Lincoln, "Fragment on Slavery," July 1854)

"Because he was so small, Stuart was often hard to find around the house."
(E.B. White, Stuart Little, 1945)

"I learned a valuable lesson about cheating after I changed a mark on my report card in the third grade."
"If a man does not keep pace with his companions, perhaps it is because he hears a different drummer."
(Henry David Thoreau, Walden, 1854)

"He was like a cock who thought the sun had risen to hear him crow."
(George Eliot, Adam Bede, 1859)

Positioning Clauses in Complex Sentences
"[D]ependent clauses cannot be sentences on their own. They depend on an independent clause to support them. The independent clause in a complex sentence carries the main meaning, but either clause may come first. When the dependent clause comes first, it is always followed by a comma."
(A. Robert Young and Ann O. Strauch, Nitty Gritty Grammar: Sentence Essentials for Writers. Cambridge Univ. Press, 2006)

The Need for Complex Sentences
"Most of the sentences we use in writing or in continuous speech are complex. . . . There is a recurrent need to expound facts or concepts in greater elaboration than the structure of the simple sentence permits."
(Walter Nash, English Usage: A Guide to First Principles. Routledge, 1986)