Question

Why do Jews write the name of God as G-d?

Answer

Why is God spelled the without an "o" throughout Jewish writings?

Any Hebrew name of God is forbidden to erase. From the Torah's exhortation to destroy idolatry, we learn out the prohibition not to destroy the name of God. (see Deuteronomy 12:3-4)

The English word "God" is actually a matter of dispute as to its degree of holiness. Many treat the name "God" with great reverence as well, for example, by spelling it with a hyphen.