What is the recommended way to create mathematical definitions?

[kedarmhaswade]

Should I proceed with the usual \usepackage{amsthm} in my main.tex (because this package has a definition environment)? Is there another way that follows the Hagenberg spirit of doing things?

[imagingbook]

HagenbergThesis has no special provision (nor "spirit") for math theorems. Just use whatever package you like and hope that it works as expected.