Who (subject pronoun) / Whom (object pronoun)
(NOTE: More often in contemporary English, Whom is abandoned and Who serves as both subject and object pronoun)
Whose (subject or object pronoun)
Whose + N (subject or object pronoun)
Which (subject or object pronoun)
Which + N (subject or object pronoun)
What (subject or object pronoun)
What + N (subject or object pronoun)
Where (subject or object pronoun)
How much/How many (subject or object pronoun)
How much/How many + N (subject or object pronoun)
Why (object pronoun)
How (object pronoun)
How + adj/adv (object pronoun)
Is it a nominal phrase (subject or object), or a question? The word order will indicate.
Could it be both a nominal phrase AND a question?
The nature of the W-word will indicate.