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phosphorus

(Encyclopedia)phosphorus fŏsˈfərəs [key] [Gr.,=light-bearing], nonmetallic chemical element; symbol P; at. no. 15; at. wt. 30.97376; m.p. 44.1℃; b.p. about 280℃; sp. gr. 1.82 at 20℃; valence −3, +3, or ...

worm

(Encyclopedia)worm, common name for various unrelated invertebrate animals with soft, often long and slender bodies. Members of the phylum Platyhelminthes, or the flatworms, are the most primitive; they are general...

ammonia

(Encyclopedia)ammonia, chemical compound, NH3, colorless gas that is about one half as dense as air at ordinary temperatures and pressures. It has a characteristic pungent, penetrating odor. Ammonia forms a minute ...

sulfur

(Encyclopedia)CE5 Sulfur crystals sulfur or sulphur sŭlˈfər [key], nonmetallic chemical element; symbol S; at. no. 16; interval in which at. wt. ranges 32.059–32.076; m.p. 112.8℃ (rhombic), 119.0℃ (mon...

vaccination

(Encyclopedia)vaccination, means of producing immunity against pathogens, such as viruses and bacteria, by the introduction of an killed or weakened microorganism, a harmless piece of a microorganism, or the like t...

X ray

(Encyclopedia)CE5 Typical X-ray composite spectrum (intensity as a function of frequency) X ray, invisible, highly penetrating electromagnetic radiation of much shorter wavelength (higher frequency) than visibl...

diving, deep-sea

(Encyclopedia)diving, deep-sea, act of descending into deep water, generally with some form of breathing apparatus, and remaining there for an extended period. It is used in fishing for sponges, coral, and pearls; ...

shark

(Encyclopedia)shark, member of a group of almost exclusively marine and predaceous fishes. There are about 250 species of sharks, ranging from the 2-ft (60-cm) pygmy shark to 50-ft (15-m) giants. They are found in ...

reproductive system

(Encyclopedia)CE5 Reproductive system reproductive system, in animals, the anatomical organs concerned with production of offspring. In humans and other mammals the female reproductive system produces the femal...

immunity

(Encyclopedia)immunity, ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian...