What is the difference between ”Father” and ”Dad”

father是父親,是比較書面和正式的說法
dad是爸爸,是比較口語和informal的說法
你可以直接叫你父親做dad(爸爸),但很少會"父親父親"這般叫他吧!

在英文來說,father只是指出一個男人在生理血緣上是孩子的父親
(A father is the male biological parent of a child, the one who gave his child genes.)
但dad是愛護孩子,照顧孩子,保護孩子,養育孩子的男人,不一定要有血緣上的關係
(A dad is a role model for a child, who spends time with them, protects, teaches and loves them unconditionally.)

這就是所謂a guy can father a child, but not any guy can be a good dad or a good parent了!

希望這些幫到你!

Father=父親 Dad=爸爸