How did the Monotype machine differ from the Linotype machine?

The primary difference between the Linotype and Monotype machines lies in how they cast type: Linotype casts an entire line of text as a single solid piece of metal, known as a slug, whereas Monotype casts individual characters in succession.123

Key operational differences include:

• Method of Composition: Linotype operators use a keyboard to select matrices that mold a full line at once. Monotype uses a two-part process: an operator types on a keyboard to create a perforated paper ribbon, which is then fed into a separate caster that reads the ribbon to produce individual pieces of type.123
• Versatility and Use: Linotype was faster and more efficient for setting large amounts of straight text. Monotype was more versatile and better suited for complex copy, such as mathematical equations or chemical formulas, because it allowed for easier mixing of typefaces and special symbols.12
• Justification: Linotype justifies lines using tapered spacebands. Monotype justifies lines by calculating the width of characters in units.13

Both systems have been largely superseded by photocomposition.12