flatten

flatten — verb

1. to press, smooth, or push something so that it becomes flat or level without bum

1.verbtransitive / intransitiveB1
Definition

to press, smooth, or push something so that it becomes flat or level without bumps or raised parts, or to become flat in this way

Example

Hao flattened the wrinkled shirt by pressing it firmly with a hot iron.

flatten + object (clothing/fabric)

The cardboard box was flattened and put into the recycling bin after Baraka unpacked it.

passive construction: be flattened

Common collocations
  • flatten a box
  • flatten wrinkles
  • flatten a tire
  • flatten the carpet
  • flatten out
Synonyms
  • smooth

    focuses on removing small bumps or roughness rather than making completely flat

  • press

    emphasizes using downward force; can be gentler than flatten

  • level

    specifically means making a surface horizontal or removing height differences

Antonyms
  • inflate

    to fill with air, the opposite of flattening a tire or balloon

Grammar Patterns

flatten + object

flatten + adverb/particle (out, down)

Usage Note

Frequently used with particle adverbs like 'out' or 'down' to emphasize the action: 'flatten out the wrinkles', 'flatten down the carpet'.

Common Mistakes

She flattened the picture on the wall with a tool.
She leveled the picture on the wall with a spirit level.
'flatten' makes something flat; 'level' makes something perfectly horizontal.

2. to stop changing up or down as quickly as before, so that the rate of increase o

2.verbtransitive / intransitiveB2
Definition

to stop changing up or down as quickly as before, so that the rate of increase or decrease becomes slower and more steady

Example

House prices in Camila's neighborhood flattened after three years of fast increases.

intransitive: prices flatten

The central bank raised interest rates to flatten the rate of inflation.

transitive: flatten + rate of [something]

Common collocations
  • flatten out
  • flatten off
  • prices flatten
  • growth flattens
  • rate flattens
Synonyms
  • stabilize

    more formal; emphasizes reaching a steady state

  • level off

    the most common phrasal alternative

  • plateau

    suggests staying at a high level without further increase

Antonyms
  • surge

    to increase suddenly and quickly

  • plummet

    to fall very quickly

Grammar Patterns

flatten + noun phrase (rates, prices, growth)

flatten + out / off

Usage Note

Common with the particles 'out' and 'off' ('flatten out', 'flatten off'). Often used to describe economic data, population trends, or physical measurements that stop changing quickly.

Common Mistakes

Sales completely flattened to zero last month.
Sales leveled off last month.
'flatten' in this sense means stabilizing at a steady level, not dropping to nothing.

3. to slow down the speed at which a disease spreads, shown on a graph as a line th

3.verbtransitive / intransitiveB2
Definition

to slow down the speed at which a disease spreads, shown on a graph as a line that becomes less steep

Example

The health minister introduced free mask distribution to flatten the infection curve.

collocation: flatten the curve

A quick vaccination campaign helped Sari's city flatten the curve and reopen schools safely.

Common collocations
  • flatten the curve
  • flatten the infection curve
  • flatten the epidemic curve
Synonyms

Grammar Patterns

flatten + noun phrase (curve, infection rate)

number + flattens

Usage Note

This sense became widely used worldwide during the COVID-19 pandemic starting in 2020. It is almost always used with 'the curve' as the object, referring to the epidemic curve on a graph showing new infections over time.

Common Mistakes

The government wants to flatten the curve of crime rates.
The government wants to reduce crime rates.
'flatten the curve' in this specific sense is reserved for disease outbreaks, particularly epidemics.

4. to press a soft or bendable material so that it becomes both flat and thin at th

4.verbtransitive / intransitiveB1
Definition

to press a soft or bendable material so that it becomes both flat and thin at the same time

Example

Noor flattened the dough into a thin circle before spreading tomato sauce on it.

flatten + into + [shape/form]

The gold was flattened into a thin sheet by a machine that hammered it repeatedly.

passive: be flattened + into

Common collocations
  • flatten dough
  • flatten into a sheet
  • flatten into a circle
  • flatten clay
Synonyms
  • roll out

    specifically for dough or pastry; implies using a rolling pin

  • press out

    emphasizes using even force to spread material

  • hammer out

    for metal; suggests repeated forceful blows

Antonyms

Grammar Patterns

flatten + object

flatten + object + into + shape/form

Usage Note

This sense is distinct from the general MAKE LEVEL sense because it specifically involves reducing thickness. Typical materials include dough, clay, metal, or wax that can be pressed or rolled into a thinner shape.

Common Mistakes

She flattened the letter onto the table.
She flattened the dough onto the table.
This sense applies to soft, bendable materials that can change shape, not to flat objects like paper that are already thin.

5. to completely knock down or destroy a building, house, tree, or other large stru

5.verbtransitiveB2
Definition

to completely knock down or destroy a building, house, tree, or other large structure so that it lies flat on the ground

Example

The abandoned factory was flattened to make space for a new city park.

passive: be flattened + purpose

Typhoon winds flattened hundreds of wooden houses along the coast of Sari's province.

natural disaster + flatten + structures

Common collocations
  • flatten a building
  • flatten a house
  • flattened by a storm
  • flattened to the ground
  • completely flattened
Synonyms
  • demolish

    more formal; specifically refers to deliberate destruction of buildings

  • raze

    formal and literary; means to destroy to the ground completely

  • level

    also means destroy completely; less common in everyday speech

Antonyms
  • build

    to construct something

  • erect

    formal; to put up a structure

Grammar Patterns

flatten + object (building, house, tree)

be flattened + by + noun phrase

Usage Note

Subject is usually a natural disaster (storm, earthquake, tornado), heavy machinery, or construction crew. Frequently used in the passive voice because the focus is on the destroyed structure rather than the agent.

Common Mistakes

The workers flattened the tree with an axe.
The workers cut down the tree with an axe.
'flatten' in this sense implies complete destruction to ground level, usually by heavy machinery or natural forces, not by hand tools.
Phrasal verbs

flatten out

phrasal verb

To become level or stop increasing after a period of growth.

After rising for months, the unemployment rate finally flattened out.

The path flattened out as we reached the top of the hill.

Idioms

flatten the curve

idiom

To slow down the increase of something, like the number of sick people, so that hospitals can handle it.

The government introduced social distancing to flatten the curve of infections.

Did the new lockdown help flatten the curve of COVID-19 cases?

Word family

  • flat
    adjectiveA2
  • flat
    adverbB1
  • flat
    nounB1
  • flatly
    adverbB2
  • flatness
    nounC1

Synonym discussion

Sense: verb/1

Flatten, level, smooth, iron, and press all involve making a surface flat, but their methods and contexts differ. Flatten is the most general — it covers any action that removes bumps or reduces height, whether by pressing, rolling, or destroying. Level adds the idea of making a surface perfectly horizontal, often with a tool like a spirit level. Smooth focuses on removing small irregularities of texture rather than bulk unevenness; a surface can be smooth without being level (e.g., polished stone on a slope). Iron is specific to clothing, fabric, and a heated appliance. Press is broader than iron — it implies sustained downward force applied to anything from a shirt to flowers to tofu. For example: 'Hao flattened the cardboard box with his foot' (general). 'The carpenter leveled the shelf with a spirit level' (horizontal precision). 'Sari ironed her dress before the interview' (clothing only). 'Tanvi pressed the flowers between the pages of a heavy book' (sustained weight).

flatten ↗level ↗smooth ↗iron ↗press ↗

Common collocations

Nouns

Adverbs

Phrases

Prepositions

Etymology

Old NorseOld EnglishEnglish

Flatten comes from the adjective 'flat', which entered English from Old Norse 'flatr' meaning level or smooth, combined with the verb-forming suffix '-en' (from Old English '-nian'). The word first appeared in English around the 14th century with the physical meaning of making something flat. The figurative and economic senses developed much later, and the 'flatten the curve' usage surged during the COVID-19 pandemic of 2020.