I presume, assume, you mean, what is the meaning of a complete sentence? A complete sentence has a noun and a verb. I'm glad that I am no longer studying another language.
"The armadillo is a poor swimmer." is a complete sentence
It is a complete sentence.
Complete the sentence with "He".
Using the word "then" at the beginning of a sentence is not incorrect. However, it does not make a sentence complete. A complete sentence must have, at a minimum, a subject and a verb. "Then" is neither of those.
Yes. You would only need a period at the end of the sentence in order for it to be a complete simple sentence.
Yes, a semicolon could indeed join an incomplete sentence and a complete sentence.
Yes that is a complete sentence
No, a complete sentence needs a subject and verb at least.
No, it is not a complete sentence. It is a fragment.
No, "How quickly you learn" is a sentence fragment. It lacks a subject and verb to make it a complete sentence.
That is not a complete sentence. You need a noun and a verb for a complete sentence.
Complete sentences are a sentence with a complete thought, statement, etc. Ex: He says he will help me on my homework. (this is a complete sentence) An incomplete sentence would be: He says he. (you did not complete the thought.)