siglum

/ˈsɪɡləm/
noun
  1. A letter, symbol, or abbreviation used to represent a word or name, especially in ancient manuscripts or reference works.
    • The manuscript used a siglum like a cross to stand for the word 'Christ'.
    • In the dictionary, the siglum 'obs.' means the word is obsolete.
    • Scholars often create a list of sigla to decode old texts.
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