noun
[ U ] capital letters (= the large form of letters, for example A, B, C rather than a, b, c) :
Headings should be in upper case.
—compare lower case
► ˌupper ˈcase adjective :
upper-case letters
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WORD ORIGIN
referring originally to two type cases positioned on an angled stand, the case containing the capital letters being higher and further away from the compositor.