The international symposium “Environment/environments” aims to shed light on a concept which is nowadays at the centre of the public agenda but is usually presented as a singular term. In this form, “environment” encompasses all life-sustaining processes that must be monitored, safeguarded and restored to mitigate the damage of human action. However, in the history and philosophy of science, the notion of environment has received multiple meanings, that all highlight, throughout their diversity, the complexity of organismal response to rapid anthropogenic changes. An accurate analysis of the different instantiations of this “relational” concept is of essence to devise targeted strategies for enhancing the efficacy of such response. Thus, in biomedicine it is of essence to understand the workings of the multiple “internal environments” within the organism; in ecology, to account for the diversity of perturbing factors at different scales of ecosystems; to draw inspirations from the diversity of socio-cultural strategies in ecosystem management; and to enlarge our knowledge on the unique characteristic of quite special environments, such as marine environments or the environment of plant communities. These and others “trajectories of a concept” will make the object of the upcoming symposium.