1, with different definitions. A complex sentence consists of two or more clauses with related meanings and does not constitute a sentence. A clause is a grammatical unit with similar structure and no complete sentence mood. A simple sentence is a sentence composed of a phrase or a word, which has a specific intonation and can express a certain meaning alone. It is impossible to analyze clauses and sentences.

2. The external signs are different. There are two main forms of complex sentences. One is that two or more clauses are combined directly in a certain order, and this complex sentence has no related words. There is usually a pause between clauses in complex sentences, which is indicated by commas, semicolons or colons in writing. A simple sentence is a complete sentence, with basically no comma or semicolon in the middle.

3. Simple sentences can be divided into subject-predicate sentences and non-subject-predicate sentences. A compound sentence has only one final intonation, which is different from several consecutive simple sentences.