Typographical syntax, also known as orthotypography, is the field of microtypography that defines the meaning and rightful usage of typographical signs, notably punctuation marks, and various elements of layout such as flushing and indentation.

Orthotypographic rules vary broadly from language to language, and even from publisher to publisher. As such, they are more often described as "conventions".

While some of those conventions have ease of understanding as a justification – for instance, specifying that low punctuation (commas, full stops, and ellipses) must be in the same typeface, weight, and style as the preceding text – many are probably arbitrary.

The rules dealing with quotation marks are a good example of this: which ones to use and how to nest them, how much whitespace to leave on both sides, and when to integrate them with other punctuation marks.

Each major publisher maintains a list of orthotypographic rules that they apply as part of their house style.

See also: Typographical error