A bar or stroke is a modification consisting of a line drawn through a grapheme. It may be used as a diacritic to derive new letters from old ones, or simply as an addition to make a grapheme more distinct from others. It can take the form of a vertical bar, slash, or crossbar.

A stroke is sometimes drawn through the numerals 7 (horizontal overbar) and 0 (overstruck foreslash), to make them more distinguishable from the number 1 and the letter O, respectively. (In some typefaces, one or other or both of these characters are designed in these styles; they are not produced by overstrike or by combining diacritic. The normal way in most of Europe to write the number seven is with a bar.^[1] )

In medieval English usage, a stroke or bar was used to indicate abbreviation.^[2] For example, ⟨£⟩, the pound sign, is stylised form of the letter ⟨Ꝉ⟩ (the letter ⟨L⟩ with a cross bar).^[3]

For the specific usages of various letters with bars and strokes, see their individual articles.

• Strikethrough
• X-bar theory (formal linguistics)
• Parallel (operator)