You can use apostrophes to show that you have omitted (left out) some letters when you are joining words together. For example, you can join the words ‘you’ and ‘are’ together. You + are = you're. The ...

Grammar: Subjects, predicates, and sentences; Nouns; Verbs; Pronouns; Adjectives and adverbs; Prepositions, conjunctions, and interjections; Clauses and complex sentences; Verbals; Subject-verb ...