moon

IPA/muːn/
KK[mˈun]IPA/muːn/

moon — noun

  • moonsingular
  • moonsplural

1. the large bright object visible in the night sky that circles our planet once ea

1.nounA2
Definition

the large bright object visible in the night sky that circles our planet once each month, shining by reflected sunlight

Example

Sumin looked up at the full moon shining over the dark lake.

full moon + prepositional phrase describing scene

The moon was so bright that the children could see their shadows on the ground.

so + adjective + that-clause for degree

Common collocations
  • full moon
  • crescent moon
  • new moon
  • bright moon
  • the surface of the moon
  • walk on the moon
  • the light of the moon
Synonyms
  • satellite

    more technical; covers both natural and artificial objects

  • lunar body

    formal or scientific, rarely used in everyday speech

Antonyms
  • sun

    the star the Earth orbits, visible during the day

Grammar Patterns

the moon

a [adjective] moon

Usage Note

When referring to Earth's moon, it is almost always preceded by 'the' and capitalised as 'the Moon' in scientific writing.

Common Mistakes

I saw moon in the sky.
I saw the moon in the sky.
English requires a determiner ('the' or 'a') before 'moon' when referring to the celestial body.

2. the particular shape that the moon appears to have at a specific point in its mo

2.nounB1
Definition

the particular shape that the moon appears to have at a specific point in its monthly cycle, such as a thin curve, a half-circle, or a full circle

Example

The waning moon appeared as a thin silver sliver before sunrise.

waning moon — phase vocabulary

Joaquín checked the moon phase chart before planning his fishing trip.

moon phase — compound noun collocation

Common collocations
  • waning moon
  • waxing moon
  • new moon
  • full moon
  • half-moon
  • crescent moon
  • gibbous moon
  • moon phase
Synonyms
  • phase

    more general; refers to the stage rather than the visual shape

  • crescent

    specific to the thin curved shape, not the general concept

Grammar Patterns

a [adjective] moon — describing visible shape

Common Mistakes

The new moon is very bright.
The new moon is almost invisible.
A new moon is the dark phase when the moon is between Earth and the Sun, so it cannot be seen from Earth.

3. a natural body that orbits a planet different from Earth, kept in its path by th

3.nounB1
Definition

a natural body that orbits a planet different from Earth, kept in its path by that planet's gravity

Example

Mars has two small rocky moons named Phobos and Deimos.

planet's moons — possessive + named

Saturn's largest moon, Titan, has a thick atmosphere like Earth.

Common collocations
  • a moon of [planet]
  • Jupiter's moon
  • Saturn's moon
  • icy moon
  • small moon
  • distant moon
  • orbit a planet
Synonyms
  • natural satellite

    more formal and technical; used in scientific writing

  • satellite

    shorter but can also refer to artificial (human-made) objects

Grammar Patterns

[planet] + has/have + [number] + moon(s)

Usage Note

Countable — 'Saturn has over 140 moons.' Use 'moon' even when the object is large (e.g., 'Titan is a moon, not a planet').

Common Mistakes

Jupiter has many moon.
Jupiter has many moons.
When referring to moons of other planets, the word is countable and takes a plural form.

4. a period of about 29 and a half days that the moon takes to go through all its p

4.nounB2
Definition

a period of about 29 and a half days that the moon takes to go through all its phases from one new moon to the next

Example

The farmers planted their crops according to the cycle of the moon.

cycle of the moon — collocation for period

In many cultures, a month is loosely based on one full cycle of the moon.

Common collocations
  • cycle of the moon
  • full cycle
  • lunar cycle
  • many moons
  • new moon to new moon
Synonyms
  • lunar month

    the precise astronomical term

  • month

    different length; a calendar month is not exactly one lunar cycle

Grammar Patterns

[number] + moon(s) — as a unit of time

Usage Note

This sense is mostly used in traditional contexts, calendars, and storytelling ('many moons ago'). In modern English, 'month' is far more common for the same length of time.

Idioms

once in a blue moon

idiom

very rarely; almost never

Sumin only goes to the cinema once in a blue moon these days.

Once in a blue moon, the whole family gathers for a big reunion dinner.

over the moon

idiom

extremely happy or delighted about something

Christopher was over the moon when he received the scholarship offer.

The children were over the moon about their trip to the wildlife park.

ask for the moon / cry for the moon

idiom

to ask for something that is impossible or extremely difficult to obtain

Asking for a private office is like asking for the moon at this company.

Joaquín wanted a sports car, but his parents told him he was crying for the moon.

many moons ago

idiom

a very long time in the past, often used in storytelling

Many moons ago, this street was lined with small family-owned shops.

Soraya moved to this town many moons ago, when she was still a child.

promise the moon

idiom

to make big promises that you cannot or will not keep

Politicians often promise the moon during election campaigns.

Faisal promised the moon to win the contract but delivered very little.

ask, cry, etc. for the moon

idiom

To want something that is very unlikely or impossible to get.

Mia knew that asking for a private jet was crying for the moon.

Is it really asking for the moon to want a quiet place to study?

promise (somebody) the earth/moon/world

idiom

To make big promises that you cannot keep.

The salesman promised us the earth, but the product was useless.

Before the wedding, he promised her the moon, but he never delivered.

promise (somebody) the moon/earth/world

idiom

To make big promises that you cannot keep.

Politicians often promise the moon during campaigns, then do little.

My boss promised me the world, but I never got a raise.

moon — verb

Word family

Synonym discussion

Sense: noun/1

Taiwanese learners sometimes confuse 'moon', 'planet', and 'star' because in Chinese the character 星 appears in all three (月亮, 行星, 恆星). A moon is a natural body that orbits a planet — for example, Earth's moon orbits Earth, and Titan orbits Saturn. A planet, by contrast, orbits a star like the Sun. A star is a massive ball of burning gas that produces its own light and heat. The key difference: stars shine by themselves; planets and moons only reflect starlight. In daily conversation, 'moon' (with 'the') nearly always refers to Earth's moon, while 'a moon' can refer to any natural satellite. 'Look at the moon tonight' is about Earth's moon; 'Saturn has many moons' is about that planet's satellites.

moon ↗planet ↗star ↗

Common collocations

Nouns

  • moon landing
  • moon rock
  • moon mission
  • moon phase
  • moonlight
  • moonrise
  • moonset
  • moon surface

Phrases

  • the dark side of the moon
  • the surface of the moon
  • the orbit of the moon
  • the pull of the moon

Prepositions

  • under the moon
  • on the moon
  • by the light of the moon
  • above the moon
  • beyond the moon

Etymology

Proto-Indo-EuropeanProto-GermanicOld EnglishMiddle EnglishEnglish

The word 'moon' comes from Old English 'mōna', which traces back to Proto-Germanic '*mēnô' and further to the Proto-Indo-European root '*mḗh₁n̥s', meaning 'moon' or 'month'. The same ancient root gave rise to 'month', 'Monday', and the Latin 'mensis' (month). The idea is that the moon's cycle was the original way of measuring time. The verb senses are much newer: 'moon about' (daydream) appeared in the mid-1800s, probably from the idea of staring dreamily at the moon. 'Moon' meaning to show one's buttocks appeared in the 1960s–70s, possibly from a playful comparison of the bare round shape to the full moon.