A Sentence:

• is a group of words that expresses a complete thought that can stand alone

• contains a subject (someone or something) and a predicate/verb (what the subject is or does)

A Sentence:

• starts with a capital letter

• has spaces between each word

• ends with punctuation (period, question mark, or exclamation point)

A Fragment:

• does not have a subject

  and/or

• does not have a predicate/verb

  and/or

• does not contain a complete idea

A Run-On:

• contains several ideas that can stand on their own (independent clauses) that aren't separated by punctuation (commas, semi colons) or conjunctions (and, but, if)