Such a sentence may be of great length (as in the last example below), but its structure is usually transparent.

512. A complex sentence, in its most elementary form, consists of one simple independent (main) clause and one simple subordinate clause.

513. Both compound sentences and complex sentences admit of much variety in structure, according to the nature and the relations of the clauses that compose them.

COMPOUND COMPLEX SENTENCES

514. Any or all of the coördinate clauses that make up a compound sentence may be complex. In that case, the sentence is called a compound complex sentence.

Note. Compound complex sentences form a special class or subdivision under the general head of compound sentences.[49]

Old Uncle Venner was just coming out of his door, with a wood-horse and saw on his shoulder; and, trudging along the street, he scrupled not to keep company with Phœbe, so far as their paths lay together; nor, in spite of his patched coat and rusty beaver, and the curious fashion of his tow-cloth trousers, could she find it in her heart to outwalk him.—Hawthorne.

This sentence consists of three coördinate clauses, each independent of the others. These are joined by the coördinate conjunctions and, nor. The first and the third clause are simple, but the second clause is complex. Hence the whole forms one compound complex sentence.