i posted a reply else where, but lets do better

latin root gen , which means race, which we understand as genes and their phenotypes in common

the suffix cide means to kill

genocide means to kill a race

a genocidal phrase would be 'total nigger death' or 'kill all white people'

a genocidal behavior would be to target a race to harm them, eg jews flooding white nations with shitskins, or bombing gaza because a few people came out and harmed your friends