The sky is the upper atmosphere covering the earth.
The white light from the sun is filtered by the atmosphere to remove a larger portion of the blue wavelengths. As the blue light is scattered to a greater extent, your eyes respond to the light waves by registering larger amounts of blue light. This is why you see the sky as being blue.(noun)
An example of the sky is where people see the sun, moon and stars.
Sky is defined as to hit, throw, shoot or hang up high in the air.(verb)
An example of sky is to toss a ball above the trees.
See sky in Webster's New World College Dictionary
noun pl. skies
Origin: ME < ON, a cloud, akin to OE sceo, a cloud, OHG scuwo, shadow < IE base *(s)keu-, a cloud, OHG scuwo, shadow < IE base *(s)keu-, to cover, hide > hide, L cutis, skin, Gr skytos, leather
See sky in American Heritage Dictionary 4
noun pl. skies skies (skīz)
Origin: Middle English
Origin: , from Old Norse skȳ, cloud; see (s)keu- in Indo-European roots.
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