Real Dictionary

first name
Your first name is the first of the names that were given to you when you were born. You can also refer to all of your names except your surname as your first names.

first name in American English
given name
noun

first name in British English
noun: a name given to a person at birth, as opposed to a surname

first-name in American English
adjective: of or pertaining to one's first, or given, name; familiar; intimate
transitive verb: to address (someone) by his or her first name, esp. as a sign of informality or familiarity

first-name in British English
modifier