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

The signaling that Rosenblatt and her team described in human tissues has several things in common with electrical mechanisms Süel has described in microbes — and which appear again and again across the tree of life. —Elise Cutts, Quanta Magazine, 12 Jan. 2026

In the late nineteen-eighties, the Soviet leader, Mikhail Gorbachev, tried to modernize his regime by democratizing the political system, ending censorship, easing the Cold War with the United States, and introducing market mechanisms into the economy. —David Remnick, New Yorker, 11 Jan. 2026

However, if the PER is too high, the cost-sharing mechanism can be delayed to 2029 or 2030. —Torrey Snow, Baltimore Sun, 11 Jan. 2026

The show is now about how money affects politics and media, or the sort of quid pro quo nature or mechanism by which those two things scratch each other’s back, the transactional relationship between those spheres of influence. —Katie Campione, Deadline, 11 Jan. 2026

Word History

First Known Use

1662, in the meaning defined at sense 1a

Phrases Containing mechanism

• defense mechanism
• escape mechanism
• survival mechanism

Rhymes for mechanism

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

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