What does equilibrium mean?
Equilibrium refers to a state of balance in which opposing forces, influences, or processes counteract one another so that no net change occurs. In physics, chemistry, and economics it carries precise technical meanings: a body in equilibrium experiences no resultant force, a reversible chemical reaction reaches equilibrium when forward and reverse rates match, and markets reach equilibrium where supply equals demand. Beyond science, the word is used figuratively to describe mental and emotional steadiness — someone who keeps their equilibrium under pressure remains composed rather than rattled. Derived from Latin roots meaning 'equal' and 'balance,' the word entered English in the early seventeenth century. It belongs chiefly to formal register and appears constantly in academic and journalistic prose. Its plural is usually equilibria in scientific contexts. Equilibrium connotes stability, poise, and a hard-won harmony among competing forces.
A state in which opposing forces or influences are balanced; a stable condition resulting from the cancellation of such forces.
"The object will remain at rest while it is in equilibrium."
In chemistry and physics, this sense has precise technical definitions; the plural in such contexts is typically 'equilibria'.
A state of mental or emotional balance and composure.
"She struggled to maintain her equilibrium during the difficult negotiations."
Often used figuratively, especially in the phrase 'lose/regain one's equilibrium.'
Scientific writing favors the Latinate plural 'equilibria', while general usage accepts 'equilibriums'. Both are correct in their respective registers.
"Chemists study the equilibria established between reactants and products in solution."
The word equilibrium literally means 'equal balance' in Latin — the same root 'libra' that gave us the zodiac scales and the pound symbol £.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of equilibrium
Equilibrium comes from Latin aequilibrium, meaning 'equal balance,' formed from aequus ('equal') and libra ('balance or scales'). It entered English in the early seventeenth century, initially as a term in mechanics describing bodies whose forces were balanced. The same Latin root libra also gives English words like equinox and equilateral through the aequus element, and underlies the astrological sign Libra and the pound symbol.
How equilibrium is actually used
Equilibrium is a formal word common in scientific writing — physics, chemistry, and economics each use it as a technical term with precise definitions. In everyday speech it often appears figuratively for emotional steadiness, frequently in the phrases 'regain/restore/lose one's equilibrium.' The plural is equilibria in scientific contexts, though equilibriums is also accepted.
Easily confused with equilibrium
Equilibrium refers to balance of forces, systems, or physical states (or composure by extension), while equanimity refers strictly to mental calmness and even-temperedness.