Resistance is a broad concept describing opposition to change, flow, motion, influence or force. Depending on context it can refer to a measurable physical property, a biological trait, a pattern of individual behavior in therapy, or collective political action. Although the specifics differ, each sense shares the core idea of something that impedes or counters another process.

Physical and engineering resistance

In physics and engineering, resistance denotes opposition to the flow of a quantity such as electric current or motion. Electrical resistance quantifies how much a conductor impedes current; it follows Ohm's law in many materials and is measured in ohms (Ω). Related concepts include conductance (the inverse) and reactance (frequency-dependent opposition in alternating current). Mechanical forms of resistance include friction, drag and damping, which convert kinetic energy into heat and slow movement. Engineers measure and design against these effects when sizing components, choosing materials, or shaping bodies for lower air or fluid resistance.

Biological and medical resistance

In biology, resistance describes the ability of organisms to survive or tolerate harmful agents. Examples are antibiotic resistance in bacteria and pesticide resistance in insects. These traits arise through genetic variation and selection and pose major challenges for medicine, agriculture and public health. Strategies to manage biological resistance include stewardship of therapeutics, monitoring, and developing new treatments or integrated control methods.

Psychological and social resistance

Psychological resistance is a term used in psychotherapy for behaviors or attitudes that impede progress, such as avoidance or denial; therapists work to understand and lessen these defensive patterns. Social or political resistance refers to organized opposition to policies, occupation or injustice; it ranges from nonviolent civil resistance to armed insurgency. Historically, resistance movements have influenced political change and shaped the course of conflicts.

Common distinctions and practical points

  • Measurement: physical resistance is often quantified; biological and social resistance are measured by outcomes or prevalence.
  • Management: reducing unwanted resistance can mean using lubricants or streamlining, while managing biological resistance emphasizes prevention and alternation of treatments.
  • Related terms: resilience (ability to recover) differs from resistance (ability to withstand).

Across disciplines, understanding the sources, mechanisms and consequences of resistance helps professionals design effective responses, from circuit design and drug policies to therapeutic strategies and social movements.