what is the difference b/w a sentence and a statement ?

In any language, a ‘sentence’ is a group of words that are put together to mean something. It is the basic unit of a language and expresses complete thought. 

A sentence is called a mathematically acceptable statement if it is either true or false,but not both.

Example : The expression “Neha is a good girl” expresses a complete thought. So, it is a sentence. 

But the expression ‘Sun’ does not express a complete thought. So, it is not a sentence.