When you are in the USA, you'll often hear some invitations. Americans often invite their friends for a meal, a party (such as dancing party, birthday party, New Year's party and so on) or just coffee. They can invite friends by phone calls, sometimes they send messages or e-mails. If people want to invite others, they often say like this,“Would you like to come to my home for dinner this Saturday evening?"“This Sunday we want to have a birthday party, can you come and enjoy it?" And people often say“Sure, I'd love to. Thank you" to accept the invitation, or“Sorry"and give a reason to turn it down. They must always reply to an invitation in a polite way. Sometimes people will hear something, but not a real invitation. For example, “Please come for coffee next time." "Let's get together soon." They are not real invitations because they don't tell the real time. They just want to keep the friendship between them. When people hear them, they usually answer "Sure, that would be good." or "OK, thank you." When you hear somebody invite you, think carefully before you answer it.