Here are some key details about complex sentences:

1. Independent Clause:

   • A complex sentence includes an independent clause, which is a group of words that can stand alone as a complete sentence.
   • The independent clause expresses a main idea or complete thought.
   • Examples:
     • "She went to the library."
     • "He studied for the exam."

2. Dependent Clause:

   • A complex sentence also contains one or more dependent clauses, which cannot stand alone as complete sentences.
   • Dependent clauses function as subordinate elements and provide additional information or support for the main idea expressed in the independent clause.
   • Examples:
     • "Because she needed to do research, she went to the library."
     • "Although he was tired, he studied for the exam."

3. Subordinating Conjunctions:

   • Dependent clauses in complex sentences are usually introduced by subordinating conjunctions.
   • Subordinating conjunctions indicate the relationship between the dependent clause and the independent clause.
   • Examples:
     • "Because," "although," "if," "when," "since," "while," "unless," "where," and "as" are common subordinating conjunctions.

4. Punctuation:

   • When a dependent clause comes before the independent clause, it is usually followed by a comma.
   • However, if the dependent clause comes after the independent clause and the sentence is clear without a comma, it may be omitted.
   • Examples:
     • "She went to the library because she needed to do research."
     • "He studied for the exam although he was tired."

Complex sentences provide a way to express relationships, conditions, cause and effect, and other nuanced connections between ideas. They allow for the combination of main and supporting thoughts in a structured and coherent manner. Understanding how to construct and use complex sentences enhances the clarity and sophistication of communication.