​The `get_theme_root_uri()` function in WordPress retrieves the URI for the themes directory without a trailing slash using the `$stylesheet` variable

Checks whether the given variable is a WordPress Error.

Determines whether a user is marked as a spammer, based on user login.

Check whether a usermeta key has to do with the current blog.

Learn how to check if a plugin can be uninstalled using the WordPress `is_uninstallable_plugin()` function in this article

Determines whether a theme is technically active but was paused while loading.

​Is_taxonomy_hierarchical() is a WordPress function that checks if a taxonomy object is hierarchical or not

Determines whether the query is for an existing custom taxonomy archive page.

Determines whether the query is for an existing tag archive page.