According to some dependency grammar theories, a relative pronoun does not simply mark the subordinate (relative) clause but also may be considered to play the role of a noun within that clause. For example, in the relative clause "that Jack built" given above, the pronoun "that" may be construed to syntactically function as the object of the verb "built." Compare this with "Jack built the house after he married," where the conjunction "after" marks the subordinate clause "after he married", but does not play the role of any noun within that clause.