Meaning of INITIAL in English
(FIRST LETTER) [noun] [C] - the first letter of a name, esp. when used to represent a namePaul M. Reynolds refused to say what the initial "M" stood for.Your initials are the first letters of each of your names.He wrote his initials, P.M.R., at the bottom of the page.
Cambridge English vocab. Кембриджский английский словарь. 2012