Full Idea
Nominalism has two main versions, one which tries to 'reduce' the objects of mathematics to something simpler (Russell and Wittgenstein), and another which claims that such objects are mere 'fictions' which have no reality (Field).
Gist of Idea
Nominalism about mathematics is either reductionist, or fictionalist
Source
David Bostock (Philosophy of Mathematics [2009], 9)
Book Reference
Bostock,David: 'Philosophy of Mathematics: An Introduction' [Wiley-Blackwell 2009], p.262