What kind of parts of speech is the word 'Shadow'?

Shadow (noun): an area of darkness, caused by light being blocked by something.
Example: The children were playing, jumping on each other's shadows.

Shadow (adjective): Used in the title of important politicians in the main opposition party (= the party not in government).
Example: The Shadow Foreign Secretary. The Shadow Cabinet.

Shadow (verb): to follow someone closely:
Example: Matsuoka was shadowed by a security officer.

Shadow (verb): to spend time with someone who is doing a particular job so that you can learn how to do it:
Example: All trainees are expected to spend a week shadowing an experienced manager.

Source: Cambridge Dictionary.