Commonly used terms such as form, function, and behavior often take on varying definitions in the literature related to product design and development. This is especially true as the point of reference moves through various stages of development from conceptual design, through product disposal. This can become problematic from the standpoint of interpretation and implementation when an information model is being created that is intended to be useful to a product throughout its entire lifecycle. A product changes throughout its useful life, so a lifecycle model of a product must also be dynamic and able to grow and age with it. If this is to be the case, descriptive terms and definitions should be specific and retain their definition throughout the life of the model. In this paper, we attempt to select a set of terminology that can be uniquely descriptive of the classes needed to define a product lifecycle model. Terms such as form, function, affordance and behavior are defined within a hierarchy of a product's lifecycle development. Terminology as presented in this context becomes less ambiguous. An example of a home-shop built pendulum clock serves to illustrate the utility of this new design lexicon. The terminology outlined here may not be optimal and significant additions and alterations may be justifiably suggested; but it is hoped that this paper will begin a dialogue eventually resulting in the elimination of much ambiguity in product modeling terminology.