Complex sentence

Traditional grammars organize sentences into 4 categories:

  • Simple sentence
  • Compound sentence
  • Complex sentence
  • Compound-complex sentence

A complex sentence has just one independent clause and at least one dependent clause:

Rex barks when the postman comes.
Rex barks [INDEPENDENT CLAUSE] when the postman comes [DEPENDENT CLAUSE].
Rex [SUBJECT] barks [FINITE VERB]
when [DEPENDENT MARKER WORD] the postman [SUBJECT] comes [VERB]

AND SEE:
Richard Nordquist defines “clause
Identifying Independent and Dependent Clauses (OWL)
Clauses (Richard Nordquist at about.com)
The Main Clause (chompchomp)
Dependent Clauses: Adverbial, Adjectival, Nominal (Towson)
Clauses and Sentences (Internet Grammar of English)