Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induced changes (e.g. morphological, physiological, behavioural, phenological) that may or may not be permanent throughout an individual’s lifespan. The term was originally used to describe developmental effects on morphological characters, but is now more broadly used to describe all phenotypic responses to environmental change, such as acclimation or acclimatization, as well as learning. The special case when differences in environment induce discrete phenotypes is termed polyphenism.