The word "to prevent" means to stop something from happening or to take measures to avoid a situation. There are several synonyms for the word "prevent" such as forbid, prohibit, hinder, counteract, obstruct, avert, impede, deter, stave off, preclude, and forestall. These words indicate different levels of action and resistance to a situation. While "forbid" and "prohibit" suggest a formal, legal means of preventing something, "deter" and "forestall" imply more subtle efforts to avoid a negative outcome. Knowing synonyms for "prevent" can help to expand your vocabulary and express ideas more succinctly.