delimiter

Delimiter is a character or sequence that marks the boundary between units of data in text, source code, or data streams. Delimiters separate tokens, fields, or elements and help a parser determine where one unit ends and another begins. They can be single characters, such as a comma, space, tab, or newline, or multi-character sequences used in markup or data formats.

In text processing and data interchange, delimiters are used to demarcate fields in records. The comma is the standard delimiter in CSV files, while tab is common in TSV files. Quotation marks or escaping rules allow delimiters to appear inside data fields. Many formats also use end-of-line sequences (CRLF or LF) as record delimiters.

In programming languages and compilers, delimiters include punctuation that signals grouping and boundaries, such as parentheses, brackets, braces, and semicolons. String literals are typically delimited by quotes, and comment syntax often uses delimiter pairs or prefixes. Lexical analysis relies on delimiters to tokenize source code.

In command shells and data streams, delimiters separate commands, arguments, or records. The semicolon can terminate a statement; the pipe character denotes a one-way data channel; whitespace often splits tokens.

Choosing a delimiter requires avoiding conflicts with data content, or implementing escaping or quoting to preserve data integrity. Delimiters may be fixed, such as a single comma, or defined by more complex rules and encodings, including multi-character sequences or non-ASCII characters.

See also: tokenization, parsing, data serialization formats, quoting and escaping, line terminators, and delimiter-aware parsing.