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hydra, in zoology

(Encyclopedia)hydra hīˈdrə [key], common name for freshwater organisms in the phylum Cnidaria, which includes jellyfish, sea anemones, and corals. Hydras are widely distributed in lakes, ponds, and sluggish stre...

harrow, in agriculture

(Encyclopedia)harrow, farm implement, consisting of a wooden or metal framework bearing metal disks, teeth, or sharp projecting points, called tines, which is dragged over plowed land to pulverize the clods of eart...

horn, in music

(Encyclopedia)horn, in symphonic and chamber music: see French horn. ...

horn, in zoology

(Encyclopedia)horn, in zoology, one of a pair of structures projecting from the head of a hoofed animal, used chiefly as a weapon. In cattle, sheep, Old World antelopes, and related animals the horns are permanent ...

halo, in art

(Encyclopedia)halo, in art: see nimbus.

halo, in meteorology

(Encyclopedia)halo, in meteorology, short-lived circles or arcs, and less commonly spikes and crosses, of colored or whitish light surrounding the moon or sun or in clouds as seen from above. A halo occurs when the...

hamadryad, in zoology

(Encyclopedia)hamadryad, in zoology: see cobra.

heart, in anatomy

(Encyclopedia)CE5 Cross section of heart, with arrows indicating direction of blood flow heart, muscular organ that pumps blood to all parts of the body. The rhythmic beating of the heart is a ceaseless activit...

heath, in botany

(Encyclopedia)CE5 Rhododendron, Rhododendron maximum, a member of the heath family heath, in botany, common name for some members of the Ericaceae, a family of chiefly evergreen shrubs with berry or capsule fru...

hickory, in botany

(Encyclopedia)hickory, any plant of the genus Carya of the family Juglandaceae (walnut family); deciduous nut-bearing trees native to E North America and south to Central America except for a few species found in S...