Real Dictionary

advantage
countable noun: An advantage is a way in which one thing is better than another.
countable noun: An advantage is something that puts you in a better position than other people.
uncountable noun: Advantage is the state of being in a better position than others who are competing against you.

advantage in American English
a more favorable position; superiority
to give an advantage to; be a benefit or aid to
noun: any state, circumstance, opportunity, or means specially favorable to success, interest, or any desired end

advantage in British English
noun: superior or more favourable position or power