Someone quickly and cheerfully accepting an invitation to a wedding is an example of a person acting with alacrity.
Origin of alacrityMiddle English and Old French alacrite from Classical Latin alacritas, liveliness from alacer, lively
- Cheerful willingness; eagerness.
- Speed or quickness; celerity.
Origin of alacrityLatin alacritās from alacer lively
Coined between 1500 and 1510 from Latin alacritās, from alacer (“brisk”) + -itas (“-ity”).