Synset

one of the large alphabetic characters used as the first letter in writing or printing proper names and sometimes for emphasis
<noun.communication>   freq. cnt.: 1 freq. cnt.: 1

capital

capital letter

majuscule

upper-case letter

uppercase

sample sentences

"printers once kept the type for capitals and for small letters in separate cases
capitals were kept in the upper half of the type case and so became known as upper-case letters"