Salutation
Part of speech: noun
Definition: A greeting, salute, or address; a hello. The act of greeting. The title in your name, such as Mr, Mrs, Ms., Dr. or Rev..
Example sentence: Email is very informal, a memo. But I find that not signing off or not having a salutation bothers me.
Greeting
Part of speech: noun
Definition: A conventional phrase used to start a letter or conversation or otherwise to acknowledge a person's arrival or presence.
Part of speech: verb
Definition: To welcome in a friendly manner, either in person or through another means e.g. writing or over the phone/internet
Example sentence: I squirrel away sealed greeting cards that people give me so I can open them later when I'm having a bad day.