【Chance】 , 【accident】 , 【fortune】 , 【luck】 , 【hap】 , 【hazard】 denote something that happens without an apparent or determinable cause or as a result of unpredictable forces.

【Chance】 serves often as a general term for the incalculable and fortuitous element in human existence and in nature and is usually opposed to law (see PRINCIPLE).

【Chance】 often retains implications derived from its early association with the casting of dice or lots and the selection of one out of many possibilities by this means; consequently it may mean determination by irrational, uncontrollable forces or it may mean one possibility of success among many possibilities of failure.

【Accident】 is interchangeable with 【chance】 only when a particular event or situation is in mind. It differs from 【chance】 mainly in its emphasis on lack of intention.

【Fortune】 , owing to its historical connection with the ancient Roman goddess of 【chance】 , Fortuna, often designates the hypothetical cause of what happens fortuitously. It also often suggests qualities ascribed to the goddess (as variability, fickleness, and malignity). 【Fortune】 is also applied to the issue or outcome of an undertaking the success of which is problematical.

【Luck】 differs from 【fortune】 chiefly in its connotations. It not only lacks the dignity accruing to 【fortune】  through the latter’s mythological associations, but it is somewhat colored by its association with gambling. It is preferable in contexts where 【fortune】 would seem bookish. 【Luck】 unqualified can, however, imply success or a happy outcome, as 【fortune】 unqualified rarely does.

【Hap】 is rather neutral and commonly denotes what falls or, more often, has already fallen to one’s lot.

【Hazard】 , which basically denotes a game of dice in which the chances are complicated by arbitrary rules, is often used in place of 【accident】 , especially when there is the traceable but not predictable influence of existing conditions or of concomitant circumstances.