the amount added to the cost to determine the asking price
"The shopkeeper calculated a twenty percent markup on the wholesale cost to set the final selling price."
detailed stylistic instructions for typesetting something that is to be printed; manual markup is usually written on the copy (e.g. underlining words that are to be set in italics)
"The editor used a red pen to add detailed stylistic instructions directly onto the manuscript, indicating which words should appear in bold or italics for the final print run."
The notation that is used to indicate the meaning of the elements in an electronic document, or to dictate how text should be displayed.
"The software developer added markup to the HTML file to ensure the headings and paragraphs were displayed correctly on every browser."
In plain English: Markup is the extra amount of money added to the cost of something to make up its selling price.
"The store added a twenty percent markup to cover its operating costs."
Usage: Markup refers specifically to the code embedded within digital documents like HTML or XML to control formatting and structure rather than physical price increases. Use this term when discussing web development or file editing instead of synonyms such as "formatting" which describes only the visual result without implying underlying instructions.
The word markup comes directly from the phrase "mark up," which originally referred to adding a price increase to an item's cost. It entered English as a single term describing this specific financial practice rather than retaining its literal sense of writing marks on something.