What does the prefix mega- mean?
Mega- comes from the Greek megas, which means "great". In the metric system it means exactly one million: a unit multiplied by 1,000,000. It sits between kilo- (thousand) and giga- (billion).
ESEN
Prefix · one million / enormously large
mega-
Signals one million units or enormous size: megabyte, megawatt, megapixel, megacity.
Scientific
Written by Bryan López, English teacher · Updated
Mega- in everyday speech
In casual language, mega- is used to exaggerate the size or importance of something, without meaning exactly one million. It is like saying "huge" or "super important", similar to super- or ultra-. Look at the context: if it talks about measurements or technology, it is one million; if it talks about people, cities or events, it just means "huge".
How it is used
Attaches to units of measurement (no hyphen) and informal nouns (sometimes hyphenated):
- mega- + unit of measurement (x1,000,000)byte → megabytewatt → megawatthertz → megahertzpixel → megapixelton → megaton
- mega- + informal nounstar → megastarcity → megacityevent → mega-eventtrend → megatrend
How it is pronounced
mega-/ˈmeɡə/
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Examples
Root word
With mega-
In a phrase
- bytemegabyteAn email without attachments uses far less than one megabyte.
- wattmegawattThe solar farm generates five hundred megawatts of clean energy.
- pixelmegapixelModern smartphone cameras capture images at forty megapixels or more.
- hertzmegahertzEarly computers ran at megahertz speeds instead of today's gigahertz.
- citymegacityTokyo is the world's largest megacity, with thirty million people.
- starmegastarThe concert sold out in minutes once the megastar was announced.
- tonmegatonA megaton measures the explosive yield of nuclear weapons.
Common mistakes
megabyte and megabit are the same
megabyte (MB) = 8 megabits (Mb); they are used in different contexts
One megabyte (MB) contains 8 megabits (Mb). Internet speeds are measured in megabits per second (Mbps), while file sizes are measured in megabytes (MB). The scale difference between them is a factor of eight.
mega- always means exactly one million
mega- means exactly one million in the SI system but simply "enormous" in colloquial use
In the SI, mega- = precisely 10⁶. In everyday speech, "megastar" or "megacity" simply convey enormous scale without a precise mathematical value.
A trick to remember it
Think of something huge, bigger than big: mega- = a million, or simply huge. megabyte, megacity.
Practise what you learned
Exercise 1 · Form the word
Exercise 2 · Pick the right one
What is the difference between a megabyte and a megabit?
Exercise 3 · Pick the right one
"Tokyo, with over thirty million people, is often cited as the world's largest ___."
Frequently asked questions
What does the prefix mega- mean in English?
The prefix mega- signals one million units or enormous size: megabyte, megawatt, megapixel, megacity.
How do you pronounce mega-?
The prefix mega- is pronounced /ˈmeɡə/. For example, "megabyte".
Can you give an example of a word with mega-?
"byte" becomes "megabyte". It is a typical example of the mega- prefix.
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