This chapter emphasizes understanding and appreciation of “woody plants” – trees, shrubs, subshrubs, and more – as biological organisms, environmental lifeforms. The central point being that such an understanding bears directly on any interpretation of archaeological wood. The details provided concerning the basic morphological features and gross anatomical characteristics of woody plants serve in part also as a prelude to more in-depth discussion of wood structural and anatomical traits and variation in later chapters. Woody plants grow, rest, mature, age, flower, bear fruit, interact with neighbors, react to environmental circumstances, and respond to signals from a host of external influences. Wood, technically secondary xylem, serves major roles as part of an integrated, dynamic system of tissues that together are integral to plant physiology, health, and longevity. Trees express juvenile, mature, and senescent stages of wood development; “reaction” wood forms mainly in response to gravitational forces and is useful to distinguish branch from stem wood. The details of growth rings and other anatomical traits provide insights into important life-history events and long-term growth circumstances affecting trees. These details in turn may serve as proxy evidence of past forest structure and the bioclimatic conditions to which once living trees responded, with relevance also to human well-being and culture. Archaeological wood is thus a richly textured source of information about the past, relating the lives of ancient trees, potentially also including human influences.