# Why focus on GCD and LCM, not LCD or GCM? [closed]

Introductory Number Theory courses, and even in high school, focus on GCD and LCM. Why don't we learn more about Lowest Common Divisor and Greatest Common Multiple?

• What's the greatest common multiple of two numbers? – Henry Towsner Feb 17 '20 at 22:34

The answer is simple: because it’s trivial. LCD Will Be always 1, even if one number is 0. GCM doesn’t exist, or it’s $$\infty$$, if you prefer.