Specificity of the number of nouns in Czech and its annotation in Prague Dependency Treebank The paper focuses on the way how the grammatical category of number of nouns will be annotated in the forthcoming version of Prague Dependency Treebank (PDT 3.0), concentrating on the peculiarities beyond the regular opposition of singular and plural. A new semantic feature closely related to the category of number (so-called pair/group meaning) was introduced. Nouns such as ruce ‘hands’ or klíče ‘keys’ refer with their plural forms to a pair or to a typical group even more often than to a larger amount of single entities. Since pairs or groups can be referred to with most Czech concrete nouns, the pair/group meaning is considered as a grammaticalized meaning of nouns in Czech. In the present paper, manual annotation of the pair/group meaning is described, which was carried out on the data of Prague Dependency Treebank. A comparison with a sample annotation of data from Prague Dependency Treebank of Spoken Czech has demonstrated that the pair/group meaning is both more frequent and more easily distinguishable in the spoken than in the written data.