The This ethnographic study of folk biology among the Tobelo (a West Papuan-speaking ethnic group of Halmahera Island, Maluku, Indonesia) outlines local cultural presumptions about classifying flora and fauna, describes the system of folk biological nomenclature in terms consistent with the morphology and syntax of the Tobelo language, and analyzes the local system of folk classification within a posited semantic domain of “biotic forms.”In the local linguistic context, dialectal differences, multilingualism, an apparently strict in-law name taboo, and particular speech registers for which Tobelo consider their own language inappropriate are shown to affect word formation, the adoption of foreign plant and animal names, and other aspects of ethnobiological classification. Culturally, the belief that names for plants and animals were set down by ancestors vastly more familiar with local biota than are their descendants, the notion that there is a “proper” name for virtually all easily visible plants and animals, and that much knowledge is and should remain esoteric, justify several alternative ways in which the Tobelo may reconcile individual or dialectal variation to determine “proper” details of classification consistent with these presumptions.Nomenclature is considered in detail. The importance of recognizing the lexemic status of homonymous and polysemous terms is illustrated; and means of recognizing lexemes having the same form as non-lexemic expressions are detailed. A morphosyntactic classification of lexemic types is here applied to the formation of terms in this domain.Unlabeled classes within this semantic domain (including the highest-level class BIOTIC FORM) are posited, and new methods are presented for determining and evaluating such “covert categories.” A critique of other procedures based on perceived similarities among plants and animals shows that the only local cultural significance of those classes may be their sudden appearance as a result of tests designed to find them, that similarities observed may not be those used in hierarchically relating folk taxa, and that such classes do not in any case belong in a linguistic description. From a systematic review of Tobelo lexemes it is possible to avoid these difficulties.The analysis of Tobelo folk biological classification (the system of semantic relations among usually lexically labeled classes) provides various types of evidence for the distinctiveness of a “basic” level, and details methods for distinguishing basic terms. Taxonomic relations order the set of hierarchically related folk classes into eleven levels: the widest or “basic” level, along with six above and four below. Non-“regular” elements of this folk taxonomy include nonsymmetric and disjunctive contrast, “residue” of higher-level classes, ambiguous subclass-superclass relations, and dual structural positions of a single class in the overall hierarchic structure.Also analyzed are other types of semantic relations among folk classes, including a ‘mother’-‘child’ relation among FAUNAL FORMS, crosscutting and intersecting subclasses of the basic class, and classification by growth stage and size. The Tobelo are able to use these methods of classifying local fauna and flora to justify the observed differences among themselves (or among Tobelo dialects) in how they classify the same plants and animals. They even sometimes use this classificatory system to productively predict the existence of plants and animals that have not yet been observed, much as our chemists once used the Periodic Table of the Elements to predict the existence of elements that had not been observed.Detailed folk classificatory, nomenclatural, and systematic botanical and zoological information for all recorded BIOTIC FORMS is given in the appendixes, which are based upon extensive collections of Halmaheran terrestrial and marine animals and plants, along with their associated ethnographic information.