How do children acquire ordinals? On the basis of novel Dutch data (and some sneak-peek English data), this talk will show that linguistic knowledge influences the development of ordinals, and that ordinal acquisition benefits from a transparent relationship between a cardinal numeral and the form used to express an ordinal meaning. In other words, (ir)regular ordinal forms influence the patterns we see in ordinal acquisition. This is in contrast to what has been claimed for the acquisition of cardinals: while the timing may be influenced by language-specific factors, effects of linguistic knowledge are not visible in the pattern of cardinals, as children from a variety of cultures go through the same phases when acquiring the exact meaning of cardinals (e.g. Carey 2009, Le Corre & Carey 2007, Sarnecka et al. 2007, Almoammer et al. 2013).