newtheoremstyle

newtheoremstyle is a command defined in the LaTeX kernel and various packages such as amsthm that allows authors to create custom styles for theorem-like environments. The command takes seven mandatory arguments: a name for the style, space above, space below, body font, punctuation, space after the theorem head, and the head font. The first argument names the style, for example \newtheoremstyle{definition}. The second and third arguments specify vertical spacing before and after the statement, in terms of \parsep or other spacing commands. The fourth argument applies to the body of the theorem; common choices are normal font, italic, or small‑caps. The fifth argument provides the punctuation that follows the theorem head, such as a period, colon or empty. The sixth argument allows the user to set additional space after the head before the body starts. Finally, the seventh argument sets the font of the theorem head itself, often bold or italic.

Once defined, the style is applied by commands such as \theoremstyle{definition} followed by \newtheorem or \declaretheorem. This makes it easy to maintain consistent typographic distinctions across many logical, mathematical, or explanatory statements. The flexibility of newtheoremstyle is a reason why LaTeX remains highly customizable for academic publishing.