Technical Abstract: Determining the vegetational attributes of rangelands is critical to their management. Yet incorporating vegetation structure, function, and classification into a single chapter is an ambitious goal and an attempt to blur the boundaries between classical community ecology that characterize patterns and ecosystem ecology which describe processes. These two disciplines are often non-overlapping and in some respects represent an evolution in research foci from classifying system composition to describing its function with or without regard to its composition. A narrative repeated throughout this section; however, is that scientists often do not strictly think about one aspect of vegetation independent of the others and instead merge concepts. This chapter will touch the surface of many topics (i.e. structure, function, life-history, etc.) and devotees are encouraged to seek additional reading dedicated to these individual topics. These topics are mentioned to the extent that they are relevant to the classification of plant communities. Additionally, this chapter will discuss the linkage between composition and structure. The function of vegetation is also presented as part of the ecosystem concept and developed especially as it relates to classifying species. This section on function will be linked to the previous section with discussion on the linkage between structure and function while touching on the more controversial link between composition (i.e. species diversity) and function. Then I will present vegetation classification and classification systems in general and in the specific context of rangelands revealing a comparable evolution from emphasis on composition to function. The strengths and weaknesses of various classification systems are discussed.