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• micro
  micro

  adjective

  extremely small.
• micro-
  micro-

  a combining form with the meanings “small” (microcosm; microgamete ), “very small in comparison with others of its kind” (microcassette; microlith ), “too small to be seen by the unaided eye” (microfossil; microorganism ), “dealing with extremely minute organisms, organic structures, or quantities of a substance” (microdissection; microscope ), “localized, restricted in scope or area” (microburst; microhabitat ), “(of a discipline) focusing on a restricted area” (microeconomics ), “containing or dealing with texts that require enlargement to be read” (microfilm; microreader ), “one millionth” (microgram ).
• micro–
  micro–

  A prefix that means: “small” (as in microorganism) or “one millionth” (as in microsecond).

micro

¹ American  

[mahy-kroh] / ˈmaɪ kroʊ /

adjective

1. extremely small.

2. minute in scope or capability.

3. of or relating to microcomputers.

4. of or relating to microeconomics.

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noun

micros plural

1. anything extremely small in scope or capability.

2. a microcomputer.

3. microeconomics.

micro- ² American  

especially before a vowel, micr-.

1. a combining form with the meanings “small” (microcosm; microgamete ), “very small in comparison with others of its kind” (microcassette; microlith ), “too small to be seen by the unaided eye” (microfossil; microorganism ), “dealing with extremely minute organisms, organic structures, or quantities of a substance” (microdissection; microscope ), “localized, restricted in scope or area” (microburst; microhabitat ), “(of a discipline) focusing on a restricted area” (microeconomics ), “containing or dealing with texts that require enlargement to be read” (microfilm; microreader ), “one millionth” (microgram ).

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micro ¹ British  

/ ˈmaɪkrəʊ /

adjective

1. very small

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noun

1. short for microcomputer microlepidoptera microprocessor microwave oven

micro- ² British  

combining form

1. small or minute

   microspore

2. involving the use of a microscope

   micrography

3. indicating a method or instrument for dealing with small quantities

   micrometer

4. (in pathology) indicating abnormal smallness or underdevelopment Compare macro-

   microcephaly

   microcyte

5.  μ.  denoting 10 ^–6

   microsecond

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micro– Scientific  

1. A prefix that means: “small” (as in microorganism) or “one millionth” (as in microsecond).

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Usage

What does micro- mean? Micro- is a combining form used like a prefix meaning “small.” In units of measurement, micro- means "one millionth." The form micro- is often used in a variety of scientific and technical terms. Micro- comes from Greek mīkrós, meaning “small.” The Latin equivalent of mīkrós is parvus, also meaning “small,” which is the source of terms such as parvovirus, a type of virus with a name that literally means “small poison.” To learn more, check out our entry for parvovirus. What are variants of micro-?When combined with words or word elements that begin with a vowel, micro- becomes micr-, as in micrify, which comes from the Latin equivalent of the form. Want to know more? Read our Words That Use article about micr-.

Other Word Forms

Inflected Forms

noun

• micros
  plural

Etymology

Origin of micro¹

Independent use of micro-, or shortening of words with this initial element

Origin of micro-²

< Greek: combining form representing mīkrós small

Explanation

Micro things are so small you can't see them, or reduced to a very small scale. When you study a subject like economics on a micro level, you look at individual markets instead of the whole economy. Most topics can be discussed or studied on a micro level — up close, looking at separate examples — or a macro level, stepping back to view the larger, wider picture. A change in climate is hard to see on the micro level (your state may have had a particularly cold winter), but easier on a macro level (the average temperature may still have increased over the last 100 years). Micro comes from the Greek mikros, "small."

Example Sentences

Also, management targets mid-to-high teens growth in assets under management over the medium-term, driven by micro-, small- and medium-sized enterprises and the mortgage segment.

From The Wall Street Journal • Apr. 27, 2026

“That’s their worldview, and navigating life as a Black woman, you’re going to experience micro- and macroaggressions,” she says.

From MarketWatch • Feb. 28, 2026

Yes, they’re cheap and convenient, but like a raccoon that crashes your dinner party, they get into everything: our rivers and oceans, and even our bloodstream, in the form of micro- and nano-plastics.

From Seattle Times • Apr. 19, 2024

Recent studies have found micro- and nanoplastics in water bottled in plastic, as well as in dust.

From Los Angeles Times • Mar. 7, 2024

Nothing about the micro- or macro- economic theory.

From "Flowers for Algernon" by Daniel Keyes

Related Words

• compact
• mini
• pocket
• pocket-size
• portable
• scaled-down
• small