These words describe events or conditions that cannot be prevented from happening. Inevitable , the strongest term, describes something that is bound to happen or be met with in the very nature of things.

• Pain is inevitable when one breaks a bone; By the time the helmsman realized his error, a collision was inevitable .

Inescapable is often used interchangeably with inevitable , but inescapable suggests something which may not be completely unalterable given a different set of attitudes or circumstances.

• Whereas death is inevitable , earning a living is inescapable unless one has private means or is forced to live at public expense; He felt that failure was an inescapable part of his lot in life.

When used in this context, necessary has less impact than inevitable and inescapable . Something that is necessary must logically occur because of an existing set of factors.

• Hunger and disease are necessary concomitants of war; Crowded streets and shops are a necessary part of big-city life.

Unavoidable is applied to events and conditions that are not always inevitable , but in specific instances are incapable of being shunned or evaded: Accidents on our highways may be inevitable , but a particular accident was unavoidable because of bad weather and heavy traffic.