German-speaking children between ages 2 and 3 mostly use the preposition ohne ('without') in an adult-like way, to express the absence of something. In this article we present surprising results from a corpus study suggesting that in this age group, absence can also be expressed using the sequence mit ohne 'with without'. We argue that this pattern becomes much less surprising if we assume that there is a conceptual representation independent of linguistic structure and that antonymic concepts such as that of absence (which we call sine in this article) are not represented as primitive concepts at this level--contrary to what might be suspected on the basis of monomorphemic prepositions such as German ohne. Instead, we argue that antonymic concepts like that of absence (sine) are composed of at least two units. Children's non-adult-like patterns then result from difficulties in acquiring the morphological realization of this complex concept as the monomorphemic preposition ohne. To our knowledge, our results constitute the first evidence for antonym decomposition in the case of prepositions from child language.