reinforce

reinforce — verb

1. to add extra material or support to a physical object or structure so that it be

1.verbtransitiveB1
Definition

to add extra material or support to a physical object or structure so that it becomes stronger and less likely to break or fail, for example adding steel beams to a concrete wall.

Example

The workers reinforced the old bridge with steel beams before the winter rains came.

reinforce + with + [material] for physical strengthening

Brandon reinforced the garden wall after noticing cracks spreading through the brickwork.

Common collocations
  • reinforce a wall
  • reinforce a bridge
  • reinforced concrete
  • reinforced with steel
  • reinforced glass
Synonyms
  • strengthen

    more general; 'reinforce' implies adding extra support to something that already exists

  • fortify

    stronger and suggests making something able to withstand attacks or extreme conditions

  • bolster

    suggests propping up something weak; 'reinforce' suggests the base is already solid

Antonyms

Grammar Patterns

reinforce + noun phrase + with + noun phrase

Usage Note

Frequently used with the preposition 'with' to state the material added. Past participle 'reinforced' is common as an adjective before nouns, e.g. 'reinforced concrete', 'reinforced glass'.

Common Mistakes

I reinforced the door adding a new lock.
I reinforced the door by adding a new lock.
When describing the method, use 'by + -ing', not a bare -ing clause.
The army reinforced the building.' (for adding soldiers)
The army reinforced its position with extra troops.
For military personnel, see sense 3 below.

2. to provide new information, evidence, or arguments that make an existing belief,

2.verbtransitiveB2
Definition

to provide new information, evidence, or arguments that make an existing belief, opinion, or idea seem more likely to be true or correct, for example a study that reinforces the link between diet and health.

Example

The latest study reinforces the idea that regular exercise improves memory in older adults.

reinforce + that-clause for supporting a belief

Selim's success in the competition reinforced his belief that hard work pays off in the end.

Common collocations
  • reinforce a belief
  • reinforce an idea
  • reinforce an opinion
  • reinforce the view that
  • reinforce a stereotype
  • reinforce a message
Synonyms
  • support

    less formal; 'reinforce' is stronger and suggests adding weight to something already believed

  • bolster

    suggests boosting something that may be weak; 'reinforce' implies the base is solid

  • corroborate

    more formal and limited to evidence supporting a claim; less common in everyday speech

Antonyms

Grammar Patterns

reinforce + noun phrase

reinforce + that-clause

reinforce + noun phrase + with + noun phrase

Usage Note

Subject is often an impersonal thing (study, report, event, evidence) but can also be a person. 'Reinforce' in this sense does not mean 'prove'; it means adding weight to an existing position. Distinguish from sense 1 (physical objects) and sense 3 (military).

Common Mistakes

The study reinforced the new theory.' (implies the theory was already established)
The study reinforced the existing theory with fresh evidence.
'Reinforce' works best when something already in place is made stronger, not for brand-new ideas.

3. to send extra troops, vehicles, weapons, or supplies to support a military force

3.verbtransitiveB2
Definition

to send extra troops, vehicles, weapons, or supplies to support a military force during a battle or operation, with the aim of making that force stronger and better able to continue fighting.

Example

The general ordered two battalions to reinforce the troops defending the eastern front.

reinforce + [military unit] for sending support

Noa's unit was sent to reinforce the soldiers stationed at the remote border post.

Common collocations
  • reinforce troops
  • reinforce a position
  • reinforce the garrison
  • reinforce the front line
  • reinforce defenses
Synonyms
  • support

    broader and less specific to military contexts

  • supplement

    suggests adding to an existing force without the urgency of battle

Grammar Patterns

reinforce + military noun phrase

Usage Note

The object is usually a military group (army, troops, battalion) or a strategic position (garrison, front line). Related noun form 'reinforcements' (plural) is very common in military contexts. This sense is rarely used figuratively outside military or strategy writing.

Common Mistakes

The manager reinforced the team with new staff.' (confusing with business context)
The manager expanded the team by hiring new staff.
For non-military contexts, use 'strengthen' or 'expand' rather than 'reinforce'.

4. to use rewards, praise, or positive feedback to encourage a particular behavior

4.verbtransitiveC1
Definition

to use rewards, praise, or positive feedback to encourage a particular behavior or response, making it more likely that the same behavior will be repeated in the future, for example giving a child a sticker each time they finish their homework.

Example

Teachers can reinforce good behavior by praising students when they share toys with classmates.

reinforce + [behavior] + by + -ing

The dog trainer reinforced calm behavior by giving the puppy a small treat each time it sat quietly.

Common collocations
  • reinforce behavior
  • reinforce a habit
  • reinforce a response
  • positively reinforce
  • reinforce learning
Synonyms
  • encourage

    broader and less technical; 'reinforce' implies a deliberate, systematic approach

  • reward

    focuses on the act of giving a reward; 'reinforce' includes the effect of making the behavior more likely

Antonyms

Grammar Patterns

reinforce + noun phrase + by + -ing phrase

reinforce + noun phrase + with + noun phrase

Usage Note

Common in psychology and education. The thing being reinforced is always a behavior, habit, or response — never a person. The reward is introduced with 'by' or 'with'. Distinguish from sense 2, where ideas/beliefs (not behaviors) are strengthened.

Common Mistakes

I reinforced my brother to study harder.
I reinforced my brother's study habits by praising him when he finished his homework.
The object must be the behavior or habit, not the person.

Word family

  • reinforcement
    nounB2
  • reinforcements
    nounB2
  • reinforced
    adjectiveB1
  • reinforcing
    adjectiveB2
  • reinforcer
    nounC1

Synonym discussion

Sense: verb/1

Strengthen is the most general word — it means making something stronger in any way, whether physical, emotional, or structural. Reinforce specifically means adding extra support to something that already exists, either by attaching material (physical) or providing evidence (abstract). Fortify is stronger and more defensive, suggesting measures taken to protect against attack or damage, like fortifying a castle or a city's defenses. Bolster suggests propping up or supporting something that is currently weak or under pressure, like bolstering the economy or a person's confidence. For example, a team might strengthen their position by winning matches; they reinforce it by signing new players; they fortify their defense with a strong goalkeeper; and they bolster a struggling teammate's morale with encouragement.

strengthen ↗fortifybolsterreinforce ↗

Common collocations

Nouns

Adverbs

Phrases

  • reinforce the idea that
  • reinforce a belief
  • reinforced concrete
  • reinforce good behavior

Prepositions

Etymology

LatinFrenchEnglish

Reinforce comes from the French word 'renforcer', which was formed from 're-' (again) and 'enforcer' (to strengthen). The English word first appeared in the 15th century and was originally used in military contexts before spreading to general use. The modern spelling with 'i' instead of 'e' (reinforce rather than renforce) came into regular use in the 18th century.