reaction
re·ac·tion / rēˈakshən/ • n. an action performed or a feeling experienced in response to a situation or event: Carrie's immediate reaction was one of relief. ∎ (reactions) a person's ability to respond physically and mentally to external stimuli: a skilled driver with quick reactions. ∎ an adverse physiological response to a substance that has been breathed in, ingested, or touched: such allergic reactions as hay fever and asthma. ∎ a chemical process in which two or more substances act mutually on each other and are changed into different substances, or one substance changes into two or more other substances. ∎ Physics an analogous transformation of atomic nuclei or other particles. ∎ a mode of thinking or behaving that is deliberately different from previous modes of thought and behavior: the work of these painters was a reaction against fauvism. ∎ opposition to political or social progress or reform: the institution is under threat from the forces of reaction. ∎ Physics repulsion or resistance exerted in opposition to the impact or pressure of another body; a force equal and opposite to the force giving rise to it.DERIVATIVES: re·ac·tion·ist / -nist/ n. & adj.
reaction
1. (pedol.) The degree of acidity or alkalinity of a soil, expressed as a value on the pH scale. See also ACID SOIL and ALKALINE SOIL.
2. (ecol.) In plant succession, the ability of an individual plant species or vegetation community to modify the physical environment and so favour further successional development. For example, the presence of the first colonizing plants in a hydrosere will tend to reduce water movement, favouring accelerated silting and so paving the way for plants typical of shallower water to arrive as new colonizers.
reaction
1. (pedol.) The degree of acidity or alkalinity of a soil, expressed as a value on the pH scale. See also acid soil and alkaline soil.
2. (ecol.) In plant succession, the ability of an individual plant species or vegetation community to modify the physical environment and so favour further successional development. For example, the presence of the first colonizing plants in a hydrosere will tend to reduce water movement, favouring accelerated silting and so paving the way for plants typical of shallower water to arrive as new colonizers.
reaction
1. the response to a stimulus.
2. the interaction of two or more substances that results in chemical changes in them.
3. the effect produced by an allergen (see allergy).