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skullcap vs. beanie

skullcap

[skuhl-kap] / ˈskʌlˌkæp /

noun

a small, brimless close-fitting cap, often made of silk or velvet, worn on the crown of the head, as for religious functions.
the domelike roof of the skull.
Botany. any of various plants belonging to the genus Scutellaria, of the mint family, having a calyx resembling a helmet.

beanie

[bee-nee] / ˈbi ni /

noun

a close-fitting knit cap worn in cold weather.
a small cap, brimless or with a short bill, often brightly colored, constructed of triangular pieces of cloth joined at the top by a button and popularized in the early 20th century as worn by college freshmen.