The lack of recent critiques about terminology has led to the frequent misuse or confusingly varied use of the words that are more or less specific to the field of terrestrial canopy biology. I provide definitions for ca 170 terms and subterms, with translations into four languages. Rather than limit coverage to tree crowns, I define canopy biology as the study of life within any aboveground parts of all plant communities, temperate and tropical. This broadened perspective enables ecologists to consider the entire range of challenges faced by organisms living in aboveground plant life, from just above the rhizosphere to the outer limits of plant growth into the atmosphere. Further, this redefinition may reduce the potential for anthropocentric biases in interpreting life on trees or other plants; encourage the use of alternative ecosystems for hypotheses that may be difficult to address in treetops; and promote more general conceptual thinking about life on vegetation, most notably the importance of scaling in ecology. Among the salient points in terminology: the concept of “stratification” has been criticized in part because strata have been defined many ways, but a flexible application of the word is central to its utility; the source of nutrients is pivotal in distinguishing epiphytes from parasites, rather than the more general issue of an organism's effects on its host; “hemiepiphyte,” as currently used, confounds two radically different life cycle strategies, suggesting a new term, “nomadic vine,” to describe the strategy typical of many aroids; there is a confusion in the literature caused by varied applications of the word “climb;” locomotor terms may have to be modified as more becomes known about forces underlying limb kinematics; and studies of leaping and falling organisms tend to overemphasize arbitrary distinctions between gliding and parachuting to the detriment of the more critical issue of capacity for “controlled descent.”