What is Function ?
Function is (noun) 1. a party, or a gathering of people We have two wedding functions in the main restaurant this weekend. The Prime Minister is tied up with official functions all week. 2. work done by someone or something The function of a goalkeeper is to stop the ball going into the net. What’s the function of that red switch? (verb) 1. to work The computer is still functioning well after months of constant use. 2. to function as to serve as The sofa functions as a bed if we have visitors.
source: Easier English, Student Dictionary Upper Intermediate Level