Writing Complex Sentences (note)

A complex sentence is made up of an independent clause and a dependent clause . An independent clause is a group of words that could be a sentence . e.g. "I am happy" . A dependent clause is a group of words that can not  be a sentence by itself e.g. "When i ski". A dependent clause can help form a sentence when it works with an independent clause e.g. I am happy when i ski. Other joining words are that, who, which, but, after, for, since, while, through.
Not a complex sentence : I was hungry, then I ate dinner.