Illustrated Glossary of Organic Chemistry
Although the term can have many meanings
, in general, simplified usage
in chemistry the term refers to a system that has two or more
substances (or the same substance in different physical states)
whose concentrations change with time. A system such as a chemical
reaction is said to be at equilibrium when there is no further
change in concentrations over time.
A pair of parallel, opposing arrows
is used to indicate that reactants
are part of an equilibrium. The arrows
do not necessarily mean that equilibrium has been achieved (i.e.,
that the concentrations are static).