parameter separator
Technical computing term for a character or string that separates parameters in a command, function call, or data format.
On the command line, a space is often used as a parameter separator.
区切り文字 is a more general term for a delimiter character, while 引数分離子 specifically refers to a separator between parameters or arguments.
Compound of 引数 (parameter, argument) + 分離子 (separator). The exact historical derivation is uncertain; the term is a modern technical coinage.