A purely painful emotion aroused on the apprehension of danger.
Though commonly a self-regarding emotion, fear may be aroused in behalf of others.
Fear serves for the protection of the individual, but, when excessive, may become injurious because it is physically depressing and mentally exciting, tending through undue excitement of the imagination to impair the power of reasoning and judgment.
When the use of reason is completely removed, there is rather a state of terror.
From a moral standpoint, slight fear must be ignored; grave fear must not be allowed to deter us from duty, yet there is lessened responsibility for evil done out of fear.
Fear, if of death or grave injury, is a diriment impediment to matrimony, rendering it invalid, for a contract under such conditions is no contract at all, because of lack of free consent.
New Catholic Dictionary