delimiter characters
Computing term for characters used to separate data fields, such as commas or tabs in CSV files.
In CSV files, commas are often used as delimiter characters.
区切り文字 is a more common term for 'delimiter character'; 区切り子文字 is a less frequent variant with the same meaning.
Compound of 区切り (delimitation) + 子 (child, element) + 文字 (character). The exact derivation is uncertain; it is a technical term used in computing.