I've encountered the word "peaceable", but probably have never used it in my life and don't know anyone else who has. It's old fashioned, and you can probably forget it. peaceful = general adjective for "peace". "A peaceful country doesn't fight a lot of wars." "This town is very quite and calm. There's not a lot of crime. It feels very peaceful." pacific also means peaceful, but is slightly less commonly used. It describes demeanor, or comportment more than behavior. "Even during battle, the general seemed calm, composed, and pacific, as though nothing could bother him." A pacifist is a person who refuses to participate in war. During Vietnam, some Americans went to jail rather than serve in the army and some went to Canada, because they were pacifists and refused to fight. "You know, Dude, I myself engaged in pacifism once. Not in 'nam of course." - Walter Sobchak, The Big Lebowski (best comedy ever made)