mechanism

noun

mech·​a·​nism ˈme-kə-ˌni-zəm 

1

a

: a piece of machinery (see machinery sense 1)

The camera's shutter mechanism is broken.

b

: a process, technique, or system for achieving a result

… the mechanisms of peace …

—Franklin D. Roosevelt

2

: mechanical operation or action : working sense 2

He acknowledges nothing besides matter and motion; so that all must be performed either by mechanism or by accident …

—Richard Bentley

3

: a doctrine that holds natural processes (as of life) to be mechanically determined and capable of complete explanation by the laws of physics and chemistry

4

: the fundamental processes involved in or responsible for an action, reaction, or other natural phenomenon

Meteorologists believe that this pressure jump is the mechanism responsible for storms and tornadoes.

—Think

compare defense mechanism

Examples of mechanism in a Sentence

The camera's shutter mechanism is broken.

Scientists are studying the body's mechanisms for controlling weight.

There is no mechanism in place for enforcing the new law.

a legal mechanism to prevent lobbyists from exerting unfair influence

psychological mechanisms for dealing with a tragic loss

Recent Examples on the Web

One possibility is a conventional mechanism in which vibrations of the material’s atomic lattice help electrons form pairs. — Neetika Walter, Interesting Engineering, 5 Sep. 2026

The emergency docket has become a mechanism for the Administration to create facts on the ground. — Ruth Marcus, New Yorker, 4 Sep. 2026

Some experts say the call for a temporary halt to more approvals should not be taken as a rejection of potential foreign investment in the country, but rather as a mechanism to establish clear rules, especially around transparency. — ABC News, 4 Sep. 2026

Both come from crude oil but they're refined into different products, with different combustion mechanisms and densities. — Willa Rubin, NPR, 4 Sep. 2026

Word History

Etymology

probably borrowed from New Latin mechanismus, from Greek mēchanḗ "device, contrivance, siege engine" + New Latin -ismus -ism — more at machine entry 1

First Known Use

1662, in the meaning defined at sense 1a

Phrases Containing mechanism

• coping mechanism
• defense mechanism
• escape mechanism
• survival mechanism

Rhymes for mechanism

• autism
• fascism
• racism
• sikhism
• sophism
• statism
• sufism
• thomism
• tourism
• tropism
• abolitionism
• aldosteronism

Kids Definition

mechanism

noun

mech·​a·​nism ˈmek-ə-ˌniz-əm 

1

: a piece of machinery

2

a

: the parts by which a machine operates

b

: the process, way, or system for achieving a goal

the mechanism of government

3

: the processes involved in or responsible for a natural occurrence (as evolution or an action or reaction)

Medical Definition

mechanism

noun

mech·​a·​nism ˈmek-ə-ˌniz-əm 

1

: a piece of machinery

2

a

: a bodily process or function

the mechanism of healing

b

: the combination of mental processes by which a result is obtained

psychological mechanisms

3

: the fundamental physical or chemical processes involved in or responsible for an action, reaction, or other natural phenomenon

mechanistic

ˌmek-ə-ˈnis-tik 

adjective