These words all designate a person or thing that opposes or is hostile to another person or thing. Opponent , the most general term in the group, designates a person engaged in some kind of disagreement, competition, opposition or conflict. Because of the wide range or uses for this word, it cannot be said by definition that an opponent is hostile or not hostile; only the context in question can determine this qualification.

• The two men had become fast friends when they were opponents in a chess tournament; Opponents of the proposed liquor legislation were defeated in a bitter fight on the floor of the House.

Antagonist , unlike opponent , can refer to an impersonal agent: Science and superstition are eternal antagonists . When applied to a person, antagonist suggests more hostility or sharper opposition than opponent does: His political antagonist was determined to use every possible means to defeat the sitting member’s bid for re-election. Adversary , like opponent and antagonist , is a general word with a wide range of application.

• The Crown prosecutor has a kind of intuition which makes him a formidable courtroom adversary ; The all Blacks and the Wallabies are worthy adversaries on the football field.

But usually adversary suggests a person or side that not only opposes another in fact, but does so with hostility or malignity: The two countries were ancient adversaries and had met more than once on the field of battle.

Rival and competitor both denote a person who seeks the same object or end for which another is striving; but, whereas the competitor may be impersonal and contend with no hostility, the rival is usually motivated by personal feelings that can make him inimical or malicious.

• The small shop owner often welcomes a nearby competitor to stimulate business; the two men were not only rivals for the same job but also for the same girl, a situation which caused an extreme amount of ill will between them.

An enemy is most often a person who is moved by feelings of animosity to an attempt to harm or destroy: Because of an old family feud, the two cousins were enemies from birth. But the word can suggest opposition without hostility, or merely a simple feeling of dislike.

• Smog is the enemy of healthy lungs; She seems to have more enemies than friends.

In military language, all who fight on the opposite side are referred to as enemies , or, collectively, as "the enemy." No personal animosity is implicit when the word is used in such contexts; individual ill feeling may or may not exist. Foe is very much like enemy in definition, but it is distinctly more poetical or literary in tone. It suggests a hostile spirit and purpose in all contexts except the most impersonal.

• Britain and Germany were bitter foes in two world wars; Ignorance is a foe of progress.