Part 19

Nascent. Just beginning, having special properties because of just having been released from combination.

Neap tide. The tide at which the high water mark is the lowest.

Nebular Hypothesis. The hypothesis advanced by Laplace that (in the words of F. W. Dyson) “a vast nebula--diffused tenuous matter--once extended to the confines of the solar system, and under the influence of gravitation slowly contracted.... As the contraction proceeded the rotation necessarily increased, and rings or other masses were thrown off which collected and formed planets.” Any of several more or less similar hypotheses.

Nectar. A sweet fluid produced by plants.

Neocene. Relating to the later part of the Tertiary (geological) period.

Neodymium. A metallic element. Symbol: Nd.

Neolithic. Relating to the later part of the Stone Age.

Neon. A gaseous element. Symbol: Ne.

Nerve. The rib of a leaf. A vein. One of the fibers or bundles of fibers carrying impulses of sensation and motion.

Neurosis. Activity of the nerves. A functional disease attributed to the nerves.

Neutral. Neither acid nor basic in reaction. Without sex organs.

Nickel. A metallic element. Symbol: Ni.

Niton. A gaseous element which occurs in radium emanation. Symbol: Nt.

Nitrogen. A gaseous element constituting about four-fifths of the air. Symbol: N.

Noble metals. Metals which do not oxidize in air or oxygen. Among the noble metals are gold, silver, and platinum.

Node. A knob or root or branch, where a leaf is usually borne. One of the points where the orbit of a planet or comet and the ecliptic meet. A point or line which is at rest in a vibrating body.

Normal. Conforming to a standard or type. The normal is not necessarily superior to the abnormal.

Nutritive. Of value as food.

Ohm. An electrical unit of resistance. The resistance of a circuit in which one volt produces one ampere of current.

Oligocene. Of the Tertiary (geological) period, between the Eocene and Miocene.

Ontogeny. Individual development.

Opsonic. Causing bacteria to be consumed more readily by phagocytes.

Optics. The science of light and vision.

Optimum. The environment most favorable to the growth of a plant or animal.

Ordovician. Relating to the Paleozoic (geological) period between the Silurian and the Cambrian.

Ore. A native mineral from which a metal or metals may be extracted.

Organic. Living, or derived from a living organism. Relating to all the carbon compounds except a few simple ones. Relating to an organ. Affecting the structure of an organ--of a disease, opposed to functional.

Organism. An organized being, plant or animal. A living individual.