Why does golf have negative numbers?

Answer 1

a "birdie" is 1 under par. Par = 0. So 1 under 0 = -1.

same for eagle, albatross, and a hole-in-one.

for a par 4 hole:

Hole-in-one = -3.

Eagle = -2.

Birdie = -1.

Par = 0.

Bogey = +1.

Double bogey = +2.

and so on