Numbers are a specific type of word in the Croatian language whose classification is not harmonized in language manuals. In addition to the inconsistent language norm, the questionnaires conducted so far (as part of professional and scientific papers) on the linguistic usage of numerical words in the Croatian standard language show that the respondents do not distinguish numbers from other quantifiers in use. The problem of number words in Croatian language manuals covers almost all language levels: morphological, syntactic, semantic and formative, so this type of word best shows the problem of the unfinished process of standardization of the Croatian language. The paper analyzes the classification of number words in language manuals through four components of grammar: morphology, syntax, semantics and word formation. The assumption is that inconsistent categorization of numbers is one of the main causes of incorrect use of number words in a language. The aim of this paper was to show the extent to which language manuals differ in the description of number words at the levels of morphology, syntax, semantics and word formation.