declaretheoremoptionsenvironment

The `declaretheoremoptionsenvironment` command in LaTeX is used to define custom theorem-like environments with specific styling and numbering options. It is part of the `amsthm` package, which provides enhanced theorem environments. This command allows users to create environments that behave like standard theorems, definitions, or propositions but can be customized to their specific needs.

When using `declaretheoremoptionsenvironment`, you specify a new environment name, an optional title, and a list of options that control its appearance and behavior. These options can include the theorem style (e.g., `plain`, `definition`, `remark`), whether to have a separator after the theorem name, and how to number the theorems (e.g., by chapter, section, or independently). You can also define a custom name for the theorem, such as "Lemma" or "Example."

For instance, `\declaretheoremoptionsenvironment{myenv}[My Theorem]{name=My Theorem,style=plain,numberwithin=section}` would create a new environment named `myenv`. Each instance of `My Theorem` within this environment would be styled as "plain" and its numbering would reset with each new section. The `amsthm` package handles the logic for displaying the theorem number and title according to the specified options. This command is particularly useful for complex documents with many different types of theorem-like structures that require consistent formatting and clear differentiation.