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National Safety Council

A nonprofit organization whose mission is to promote and influence safety and health at work, on the road, at home, and in the environment.

National Stroke Association

ABBR: NSA. A nonprofit organization devoted to stroke prevention, treatment, rehabilitation, and research and to the support of people who have had strokes, their partners, and their families. Telephone: STROKES; Website:

National Student Nurses Association

ABBR: NSNA. The primary organization for student nurses in the U.S., a counterpart of the American Nurses Association.


(nā′tĭv) [L. nativus] 1. Born with; inherent. 2. Natural, normal. 3. Belonging to, as place of one’s birth.

native language

The first language a person learns. It is usually the language he or she is most proficient in and uses with the greatest comfort, confidence, and precision. SYN: first language; mother tongue.


(nă-trē′mē-ă) [L. natrium, sodium, + Gr. haima, blood] Sodium in the blood.


(nā′trē-ŭm) [Ult. fr. Gr. natron + -ium (1)] SYMB: Na. SEE: sodium.


(nā″trē-ū-rē′sĭs) [″ + Gr. ouresis, make water] The excretion of abnormal amounts of sodium in the urine.


(nā″trē-yŭ-ret′ik) [natrium + Gr. ourētikos, pert. to urine] 1. Pert. to the excretion of sodium in the urine. 2. Any substance that increases sodium excretion by the kidney. SYN: saluretic. SEE: diuretic.


[L. natura, nature] Not abnormal or artificial.

natural childbirth

SEE: under childbirth.

naturalistic fallacy

The belief that any natural product is safe, effective, and good for one’s health. It is sometimes associated with the belief that any artificial product is unhealthy.

natural killer cell

SEE: natural killer cell.

naturally occurring retirement community

ABBR: NORC. An unplanned community in which at least 40 percent of the heads of households are over 60. NORCs form when a large number of young people move into a community and grow old there, when a large number of seniors move into a community, or when seniors remain in a community as younger people move out.

natural selection

SEE: under selection.

nature and nurture

The combination of a person’s genetic constitution and the environmental conditions to which he or she is exposed. The interplay of these forces produces physical and mental characteristics that make each human being different from every other.


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