olemus
ISO/IEC 2382:
kirjamärk, mis pole täht, number ega tühimärk
ja mis tavaliselt pole ideogramm
=
graphic character that is not a letter, digit, or blank character, and usually not an ideogram

näiteid
https://www.yourhtmlsource.com/text/specialcharacters.html

https://docs.oracle.com/cd/E11223_01/doc.910/e11197/app_special_char.htm#MCMAD416

https://askubuntu.com/questions/562026/special-characters-for-libreoffice