A sentence is a group of words consisting of a subject and predicate.(noun and verb) A statement can be a sentence if asserting something either verbally or written. However statement has other meaning in English. A person can make a statement without any words. i.e. She died her hair blue and pierced her ears to make a statement to her parents.(The statement being that she is independent and can make her own decisions.) Also statement can be a synonym for an bill received at regular intervals from a company. i.e. I received my bank statement or I received my phone statement.

sentence : a group of words, usually containing a verb, which expresses a thought in the form of a statement, question, instruction, or exclamation and starts with a capital letter when written: statment :something that someone says or writes officially, or an action done to express an opinion: