hap·py
Pronunciation: 'ha-pE
Function: adjective
Inflected Form(s): hap·pi·er; -est
Etymology: Middle English, from hap
Date: 14th century
1 : favored by luck or fortune : FORTUNATE
2 : notably fitting, effective, or well adapted : FELICITOUS
3 a : enjoying or characterized by well-being and contentment : JOYOUS
b : expressing or suggestive of happiness : PLEASANT
c : GLAD, PLEASED
d : having or marked by an atmosphere of good fellowship : FRIENDLY
4 a : characterized by a dazed irresponsible state
b : impulsively or obsessively quick to use or do something
c : enthusiastic about something to the point of obsession : OBSESSED
synonym: see LUCKY, FIT

from: merriam webster's collegiate dictionary