Množina: aurochs

ETYM German auerochs, Old High Germ. ûrohso; ûr (cf. AS. ûr) + ohso ox, German ochs. Related to Owre, Ox.
(plural aurochs) Extinct species of long-horned wild cattle Bos primigenius that formerly roamed Europe, SW Asia, and N Africa. It survived in Poland until 1627. Black to reddish or gray, it was up to 1.8 m/6 ft at the shoulder. It is depicted in many cave paintings, and is considered the ancestor of domestic cattle.
Large recently extinct long-horned European wild ox; considered one of the ancestors of domestic cattle; SYN. urus, Bos primigenius.
Extinct wild ox.

Množina: auroras

ETYM Latin aurora, for ausosa; Skr. ushas, and Eng. east.
Dawn; reddish glow in sky before sunrise. aurora borealis, luminosity in sky in Arctic region due to atmospheric electricity; northern lights. aurora australis, same phenomenon in Antarctic region; southern lights.
Colored light in the night sky near the Earth’s magnetic poles, called aurora borealis (“northern lights”) in the northern hemisphere and aurora australis in the southern hemisphere. Although aurorae are usually restricted to the polar skies, fluctuations in the solar wind occasionally cause them to be visible at lower latitudes. An aurora is usually in the form of a luminous arch with its apex toward the magnetic pole followed by arcs, bands, rays, curtains, and coronas, usually green but often showing shades of blue and red, and sometimes yellow or white. Aurorae are caused at heights of over 100 km/60 mi by a fast stream of charged particles from solar flares and low-density “holes” in the Sun’s corona. These are guided by the Earth’s magnetic field toward the north and south magnetic poles, where they enter the upper atmosphere and bombard the gases in the atmosphere, causing them to emit visible light.
The French philosopher Gassendi coined the term “northern dawn” 1621.
An atmospheric phenomenon consisting of bands of light caused by charged solar particles following the earth's magnetic lines of force.

Množina: aurora australis

The aurora of the southern hemisphere; SYN. southern lights.
An aurora that occurs in earth's southern hemisphere — called also southern lights.

Množina: aurora borealis

The aurora of the northern hemisphere; SYN. northern lights.
An aurora that occurs in earth's northern hemisphere — called also northern lights.

1. Characteristic of the dawn; SYN. aurorean.
2. Of or relating to the atmospheric phenomenon auroras.