sky
/skaɪ/·스카이·noun
the space above the earth
NorseCEFR A1
Root
Old Norse 'ský' (cloud)
Old Norse ský (cloud) → Middle English sky (originally 'cloud', later 'firmament')
In a word
Curiously, sky first meant "cloud". The Old Norse ský entered English through Viking contact. In Middle English the meaning widened from cloud to the whole firmament. Meanwhile the Old English heofon narrowed into the religious heaven — one spot, two words can't share it.
Examples
The sky was clear and blue.
Birds fly across the sky.
A star shone in the night sky.
Related
skylineskyscraperskywardskylight