Bibliography notation is a system of abbreviations used to cite sources in academic writing. IBID (4 letters) is an abbreviation for the Latin term 'ibidem, ' which means 'in the same place.' ETAL (4 letters) is an abbreviation for the Latin term 'et alii, ' which means 'and others.' IDEM (4 letters) is an abbreviation for the Latin term 'IDEM, ' which means 'the same.' ETALII (6 letters) is an abbreviation for the Latin term 'et alii alteri, ' which means 'and others of a different kind.'