Simple I believe. In a simple sentence, always look for a subject and a verb. Also, make sure there are NO conjunctions. In complex sentences, always look for subordinating conjunctions, such as when, since, or once. In compound sentences, my teachers have told me to remember FANBOYS (for, and, nor, but, or, yet, so.) In compound-complex sentences, look for both types of conjunctions. Also, a complex sentence will usually always have a independent and dependent clause. An independent clause is a part of a complex sentence that can stand in its own at a complete thought. A dependent clause could NOT stand on its own as a complete thought. A compound sentence always has two sentences conjoined with one of the FANBOYS.
Example of a complex sentence: Once we leave, we can go to the park.
‘Once we leave,’ is and dependent clause. It can not stand on its own as a complete thought. A complete thought always has a subject (noun or a pronoun), and a verb (an action). ‘We can go to the park.’ CAN stand as a complete thought. ‘We’ is your subject, and ‘go’ is your verb.
I really hoped this helped you!! You may want to ask someone else for verification, but this is what I’ve always been taught.
