significant SGML character
Technical computing term referring to characters with special meaning in SGML parsing, such as '<', '>', and '&'. Rare outside markup language documentation.
In SGML, significant SGML characters must be represented using entity references.
The markup language itself; 重要なＳＧＭＬ文字 refers specifically to the characters that have syntactic meaning within SGML.
Entity reference; the mechanism used to escape significant SGML characters in SGML documents.
A compound of 重要な (important) + ＳＧＭＬ (SGML) + 文字 (character), directly calqued from the English computing term 'significant SGML character'.