ion

IPA/ˈaɪən/

KK[ˈaɪən]IPA/ˈaɪən/

ionsingular
ionsplural

1.nounB2

Definition

a microscopic unit consisting of one atom or several atoms bound together, which becomes electrically charged whenever it gains extra electrons or loses some of its own

Example

In class, Walid drew a diagram showing how a sodium atom becomes a positive ion.

countable noun with 'a'

Lithium ions in a battery move from the negative toward the positive electrode during use.

noun + 'ions' as subject in technical context

Common collocations

positive ion
negative ion
lithium ion
hydrogen ion
ion exchange
ion channel

Usage Note

In scientific writing, the specific charge is often stated: a positive ion (cation) loses electrons, while a negative ion (anion) gains electrons. The noun is also used in compound terms such as lithium-ion battery or ion channel.

Common Mistakes

An ion is the same as an atom.

An ion is an atom or group of atoms that has gained or lost electrons, giving it a charge.

Not all atoms are ions; only charged atoms are ions.

Salt water contains free ions just floating alone.

When salt dissolves, its crystals split into separate positive and negative ions.

Ions pair up in crystal form; they separate only when dissolved or melted.

IPA/-ən/

KK[ˈaɪən]IPA/-ən/

1.suffixB1

Definition

used after a verb to create a noun that names the action or the process of doing what the verb describes

Example

The construction of the new school took nearly eighteen months to finish.

construct → construction (action)

Nadia's translation of the Japanese poem captured its original rhythm and feeling.

translate → translation (process)

Grammar Patterns

verb + -ion/-tion/-sion/-ation → noun

Usage Note

The suffix takes several spelling forms depending on the ending of the verb: -tion (after most verbs ending in -t: act → action), -sion (after verbs ending in -d or -s: decide → decision), -ation (after verbs ending in -e or -ize: explore → exploration), and -ition (with some verbs: add → addition). These are not predictable by rule, so learners should check each word in a dictionary.

Common Mistakes

The discution went on for hours.

The discussion went on for hours.

The verb 'discuss' takes the -sion form, not -tion.

2.suffixB1

Definition

used after a verb to create a noun that refers to the thing that is produced or achieved by an action or process

Example

Jin's invention was a simple tool that helps farmers water their crops using sunlight.

invent → invention (thing produced)

The illustration in the biology textbook showed the different parts of a flower.

illustrate → illustration (produced image)

Grammar Patterns

verb + -ion/-tion/-sion → noun (result)

Usage Note

This sense overlaps with sense 1 (ACTION OR PROCESS). The difference is focus: sense 1 emphasizes the activity itself (The construction took a year), while this sense emphasizes the finished product (The construction is a tall building). Many -ion nouns can carry both meanings depending on context.

3.suffixB1

Definition

used after a verb to create a noun that describes a state, quality, or condition resulting from an action or feeling

Example

Élise felt a deep sense of satisfaction after finishing her first marathon race.

satisfy → satisfaction (inner state)

The confusion in the classroom grew as the teacher's instructions became more complicated.

confuse → confusion (mental state)

Grammar Patterns

verb + -ion → noun (state/condition)

Usage Note

Many -ion nouns expressing state or condition overlap with -ment and -ness nouns (e.g., satisfaction, enjoyment, happiness). The -ion form is generally preferred in more formal or academic writing, while -ness often sounds more natural in everyday conversation.

Word family

ionic
adjectiveC1
ionize
verbC1
ionization
nounC1
ionizer
nounC1
anion
nounC1
cation
nounC1

Synonym discussion

Sense: noun/1

An ion, an atom, a molecule, and a particle are all small units of matter, but they differ by charge and composition. An atom is the basic unit of a chemical element (e.g., a single oxygen atom), electrically neutral unless it has gained or lost electrons. A molecule is two or more atoms bonded together (e.g., H₂O). An ion is specifically an atom or molecule that carries an electric charge because its number of electrons does not equal its number of protons. A particle is the broadest term, referring to any tiny piece of matter, from a single electron to a speck of dust. For example, a sodium atom (neutral) becomes a positive ion when it loses one electron, and that ion is also a particle, but not all particles are ions.

atom ↗molecule ↗particle ↗

Common collocations

Nouns

exchange (ion exchange)
channel (ion channel)
beam
source
battery (lithium-ion battery)

Phrases

positive ion
negative ion
charged ion
free ion
ion pair

Prepositions

of (ions of sodium)
in (ions in solution)

Etymology

GreekEnglish

The word 'ion' was coined in 1834 by the English scientist Michael Faraday. He took it from the Greek word 'ion,' meaning 'going,' which is the neuter present participle of 'ienai' (to go). Faraday chose this name because ions are particles that move — or 'go' — toward an electrode when an electric current passes through a solution.

First known use

1834

1834, in the meaning defined at sense 1

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ion

ion — noun

1. a microscopic unit consisting of one atom or several atoms bound together, which

Usage Note

Common Mistakes

ion — abbreviation

1. a short written form of the word Ionic, used to refer to a classical style of Gr

Usage Note

ion — suffix

1. used after a verb to create a noun that names the action or the process of doing

Grammar Patterns

Usage Note

Common Mistakes

2. used after a verb to create a noun that refers to the thing that is produced or

Grammar Patterns

Usage Note

3. used after a verb to create a noun that describes a state, quality, or condition

Grammar Patterns

Usage Note

Word family

Synonym discussion

Common collocations

Nouns

Phrases

Prepositions

Etymology

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