survival

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or process of surviving.
• noun The fact of having survived.
• noun Something, such as an ancient custom or belief, that has survived.

from The Century Dictionary.

• noun The act of surviving or outliving; a living beyond the life of another person; in general, the fact of living or existing longer than the persons, things, or circumstances which have formed the original and natural environment: often specifically applied to the case of a rite, habit, belief, or the like remaining in existence after what justified it has passed away.
• noun One who or that which thus survives, outlives, or outlasts.
• noun In biology, the fact of the continued existence of some forms of animal and vegetable life after the time when certain related forms have become extinct; also, the law or underlying principle of such continued existence, as by the process of natural selection: in either case more fully called survival of the fittest, and by implication noting the extinction of other organisms less fitted or unfit to survive the struggle for existence.

from the GNU version of the Collaborative International Dictionary of English.

• noun A living or continuing longer than, or beyond the existence of, another person, thing, or event; an outliving.
• noun (Arhæol. & Ethnol.) Any habit, usage, or belief, remaining from ancient times, the origin of which is often unknown, or imperfectly known.
• noun (Biol.) See Natural selection, under Natural.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The fact or act of surviving; continued existence or life.
• noun as a modifier Of, relating to or aiding survival.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a natural process resulting in the evolution of organisms best adapted to the environment
• noun something that survives
• noun a state of surviving; remaining alive