One (simple) example: My mother cooked a rich, flavorful dish made of pinto beans and brown rice.
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A complete sentence has a subject and a verb that creates a complete thought.
In that sentence, we have a very long subject: A rich, flavorful dish made of pinto beans and brown rice. However, we're missing a verb. You can add any verb (and other details) you like and make it as long as you want to.
