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perturb

/pərˈtɜːrb//pəˈtɜːb/·verb
to disturb a system or a person's calm, knocking it off its steady state
Fig. 1 — A compass needle rests dead steady on north, the whole instrument at peace.
01Definition

To perturb something is to disturb it — to knock a settled system, orbit, or state of mind off its balance. From Latin perturbare, 'to throw into confusion', it is a favourite of science: a planet's path is perturbed by a passing mass, and a chemical equilibrium is perturbed by heat. Applied to people it is formal and usually negative — to be perturbed is to be unsettled or quietly worried, not merely surprised. The disturbance is often small, but it is enough to make a stable thing wobble.

02In use
  • iA single careless remark was enough to perturb the otherwise serene meeting.
  • iiAdd heat and you perturb the equilibrium, and the readings begin to fluctuate.
  • iiiThe astronomers watched the comet's orbit perturb slightly as it neared the planet.
03Collocations
  • perturb the system
  • deeply perturbed
  • perturb the equilibrium
  • visibly perturbed

Family perturbation (noun) · perturbed (adjective)

04Relations

=disturb, unsettle, disquiet, agitate, ruffle

≠calm, settle, reassure

06TOEFL & IELTS

Useful in TOEFL science lectures (orbital and chemical 'perturbation') and in IELTS as a formal alternative to 'upset' or 'worry' ('investors were perturbed by the figures'). Stress falls on the second syllable, per-TURB, and the noun perturbation appears in academic reading far more often than the verb.

07Asked
What is the difference between perturb and disturb?
Disturb is the broad, everyday word — you can disturb a sleeper, a meeting or the peace. Perturb is its formal, precise cousin with two homes: systems and minds. A force perturbs an orbit or an equilibrium; bad news perturbs a person into quiet, continuing worry. The scene above holds the core: one pass of the magnet, and a settled needle is left hunting for its bearing.
What does perturbed mean?
Unsettled and anxious — knocked off your calm rather than merely annoyed. It is the form you actually meet: the perturbed form far outnumbers the bare verb in modern prose, often intensified — deeply perturbed, visibly perturbed. The register is formal and the feeling contained: a perturbed person is worried behind a composed face, not shouting.
Is unperturbed the opposite of perturbed?
Yes — and a busy word in its own right: to remain unperturbed is to stay calm exactly where perturbation was expected — a pilot unperturbed by the warning light. It is quiet praise, close to unruffled. Note the geometry: unperturbed describes the person the disturbance failed to move, not the absence of any disturbance at all.
What is a perturbation in science?
A small outside influence that nudges a system away from its steady state — and a workhorse concept: astronomers found Neptune by working backwards from unexplained perturbations in Uranus's orbit. The method matters as much as the word: start from a problem you can solve exactly, add the small disturbance, and calculate how the answer shifts. Stress moves in the noun: per-tur-BAY-shun.