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://duckduckgo.com/?t=h_&q=%22special+characters%22&iax=images&ia=images