Data from a representative sample of the world's languages indicate that adjectives only occur in languages in which the numeral is in a direct construction with a noun (i.e. the numeral does not occur with a sortal classifier). In my sample Hmong Njua is the only counterexample, but I will show that Hmong Njua classifiers have assumed other functions and that the language has developed some kind of regular number marking (which is unusual for a classifier language). This suggests that Hmong Njua does not use the kind of noun that is commonly employed in a classifier language. Ultimately I will argue that the occurrence of adjectives as a major word class is not so much related to the absence of classifiers, but rather depends on a semantic property of the nouns in that language. A language can only have adjectives if the nouns in that language are lexically specified for the feature [+Shape], which means that the properties that are designated by these nouns are characterized as having a spatial boundary.