compound

compound — noun

IPA/ˈkɒmpaʊnd/
KK[kˈɑmpaʊnd]IPA/ˈkɑːmpaʊnd/
  • compoundsingular
  • compoundsplural

1. a material created when atoms from several different chemical elements bond toge

1.nounB2
Definition

a material created when atoms from several different chemical elements bond together in a fixed ratio by weight

Example

Caio's science class studied how sodium and chlorine join to form the compound known as table salt.

collocation: form a compound

Water is a simple compound made of two hydrogen atoms linked to one oxygen atom.

Common collocations
  • organic compound
  • chemical compound
  • form a compound
  • synthetic compound
  • compound molecule
Synonyms
  • substance

    broader; any kind of material, not necessarily chemically bonded

  • material

    even broader; refers to what something is made of

  • chemical

    can refer to any chemical substance, including pure elements

Antonyms
  • element

    a pure substance made of only one type of atom, not chemically combined

Usage Note

Common in chemistry contexts. Often used with the verb 'form': 'Sodium and chlorine form a compound.'

Common Mistakes

Water is a mix of hydrogen and oxygen.
Water is a compound of hydrogen and oxygen.
a 'mix' can have any proportion; a 'compound' has a fixed chemical formula.

2. something created by combining several separate elements, such as ingredients, q

2.nounB2
Definition

something created by combining several separate elements, such as ingredients, qualities, or components

Example

The sauce is a delicious compound of tomatoes, fresh herbs, and olive oil.

compound of [ingredient 1] + [ingredient 2] + [ingredient 3]

Hoa's breathing problems were caused by a compound of dust, smoke, and pollen in the air.

Common collocations
  • compound of
  • rich compound
  • complex compound
Synonyms
  • combination

    more general; does not imply the parts blend into a single thing

  • mixture

    parts are physically combined but not chemically bonded

  • blend

    suggests the parts are smoothly mixed, often of liquids or flavours

  • composite

    emphasises that the parts remain separately identifiable

Common Mistakes

The air is a compound of gases.' (in everyday speech)
The air is a mixture of gases.
'compound' in everyday use is less common than 'mixture' for non-chemical combinations.

3. a term formed by joining several existing words together, which can be written a

3.nounB2
Definition

a term formed by joining several existing words together, which can be written as a single unit, separate items, or linked by hyphens

Example

Kian learned that 'mother-in-law' is a hyphenated compound in English grammar.

hyphenated compound

The word 'bus stop' is a compound noun written as two separate words.

Common collocations
  • compound noun
  • compound word
  • hyphenated compound
  • closed compound
  • open compound
Synonyms
  • portmanteau

    blends parts of two words, like 'brunch' from 'breakfast' + 'lunch'; narrower than compound

  • derivative

    formed by adding prefixes or suffixes, not by joining whole words

Usage Note

The spelling of compound words varies: closed (bedroom), open (bus stop), or hyphenated (mother-in-law). Learner dictionaries mark this in each entry.

Common Mistakes

Firefly is a compound word.' (stating only the fact)
The compound firefly is a word formed from fire and fly, but it refers to an insect, not a burning fly.
learners benefit from knowing how the parts relate to the meaning.

4. a walled or fenced piece of land containing several buildings, often forming a s

4.nounB2
Definition

a walled or fenced piece of land containing several buildings, often forming a single secure site

Example

The embassy compound was surrounded by tall concrete walls and security cameras.

embassy compound with security walls

The Watanabe family lived inside a large compound with several smaller houses and a garden.

Common collocations
  • embassy compound
  • military compound
  • temple compound
  • prison compound
  • guarded compound
  • wall around a compound
Synonyms
  • enclosure

    more general; can be a small fenced area without buildings

  • complex

    a group of buildings, but not necessarily walled or enclosed

  • campus

    a university or company site, typically open rather than walled

Usage Note

Often used for embassies, military bases, prisons, temples, schools, or family estates. Suggests some level of security or separation from the outside.

Common Mistakes

Our school is in a compound.' (for a single building on an open campus)
Our school is in a compound surrounded by a wall.
add a detail that shows the boundary.

compound — verb

IPA/kəmˈpaʊnd/
KK[kəmpˈaʊnd]IPA/kəmˈpaʊnd/

compound — adjective

IPA/ˈkɒm.paʊnd/
KK[kˈɑmpaʊnd]IPA/ˈkɑːm.paʊnd/

Word family

Synonym discussion

Sense: noun/2

All five words describe things made from more than one part, but they differ in how the parts relate. Compound suggests a close, often chemical-like union where the parts together form a single new thing — a compound of flavours in a sauce. Mixture is looser: the items keep their separate identities (a mixture of nuts and raisins). Blend implies smooth, even mixing, especially of liquids or abstract qualities (a blend of cultures). Combination is the most general — simply two or more things brought together, with no claim about how they interact (a combination of factors). Composite emphasises that the parts remain detectable within the whole (a composite photograph made from several images). For everyday use, when you want to say something is made of several ingredients that work together, compound fits well. For a casual list of items, mixture or combination sounds more natural.

compound ↗mixture ↗blend ↗combination ↗composite ↗

Common collocations

Nouns

  • compound problem
  • compound interest
  • compound word
  • compound eye
  • compound fracture

Adverbs

  • chemically compound
  • financially compound
  • further compound

Phrases

  • compound the situation
  • compound an error
  • compound annual growth rate

Prepositions

  • compound of
  • compound from
  • compound with

Etymology

LatinOld FrenchEnglish

The word 'compound' arrived in English through Old French 'compoudre' (to mix together), which came from Latin 'componere' — a combination of 'com-' (together) and 'ponere' (to put or place). The original meaning was simply 'to put together', which still runs through all modern senses: chemical compounds are atoms put together, compound words are words put together, a compound (enclosure) is a place where buildings are put together behind walls, and to compound a problem is to put additional difficulty on top of an existing one.