S: (v) prevent, keep (stop (someone or something) from doing something or being in a certain state) "We must prevent the cancer from spreading"; "His snoring kept me from falling asleep"; "Keep the child from eating the marbles"
S: (v) intervene, step in, interfere, interpose (get involved, so as to alter or hinder an action, or through force or threat of force) "Why did the U.S. not intervene earlier in WW II?"