Use 's at the end of a word when you want to do one of these things:
1. Use the short form of is. Instead of “Godzilla is angry,” you can write “Godzilla’s angry.” The apostrophe shows that the letter i is missing.
Note: this use is informal; do not use 's in this way in formal writing.
2. Use the short form of has when has is the helping verb in a present perfect verb construction. Instead of “Godzilla has just destroyed a bridge,” you can write “Godzilla’s just destroyed a bridge.” The apostrophe shows that the letters h and a are missing.
Note: this use is also informal; do not use 's in this way in formal writing.
3. Write the short form of us in the construction “let’s” when you are making a suggestion. “Let us” is very formal and we don’t say or write it now, but we write the apostrophe in “let’s” to show that the letter u of the old form “let us” is missing. For example, “Let’s watch a Godzilla movie tonight!”
4. Show possession (ownership). Instead of “Godzilla pulled down the electric lines of Tokyo,” you can write “Godzilla pulled down Tokyo’s electric lines.” The electric lines belong to Tokyo.
Note: do not use 's to show possession with personal pronouns (I, you, he, she, it, we, they). Personal pronouns have their own possessive forms: my, your, his, her, its, our, their.
it’s = it is, for example “It’s really scary when Godzilla comes to town.”
it’s = it has, for example “It’s been fun watching a Godzilla movie.”
its = something belongs to it, for example “When Godzilla left, Tokyo was dark. Its electric lines were destroyed.”
Do NOT use 's when you want to do one of these things:
1. Make a noun plural (more than one). Write “Godzilla has destroyed many subway trains,” not “Godzilla has destroyed many subway train’s.”
2. Write a third person singular (he/she/it) verb. Write “Godzilla lives in the sea,” not “Godzilla live’s in the sea.”