based

based — adjective

1. If something is based on something else, it uses that thing as its starting poin

1.adjectiveB1
Definition

If something is based on something else, it uses that thing as its starting point, main idea, or source material.

Example

Lakshmi's novel is based on true events from her grandmother's childhood.

based on [source material]

The board's final decision was based upon a careful review of all the evidence.

based upon [formal alternative]

Common collocations
  • based on evidence
  • based on fact
  • based on research
  • based on experience
  • based on a true story
Synonyms
  • founded on

    Emphasises the idea of being built upon a strong foundation, often for institutions or abstract concepts

  • derived from

    Focuses on the idea of coming from a source, typically for words, substances, or data

  • grounded in

    Suggests a deep, solid connection to facts or principles; more formal

Antonyms
  • unfounded

    Describes a claim or idea that has no basis at all — opposite of being supported by evidence

Grammar Patterns

based on [noun/phrase]

based upon [noun/phrase]

Usage Note

Always followed by 'on' (or 'upon' in more formal English). Cannot be used directly before a noun — 'a based-on-facts report' is incorrect; use 'a report based on facts' instead.

Common Mistakes

The movie was based of a true story.
The movie was based on a true story.
Use 'on', not 'of', after 'based'.
This is a based-on-research paper.
This paper is based on research.
'Based on' cannot be placed before a noun like a single adjective.

2. A particular place serves as a person's or organization's main home, office, or

2.adjectiveB1
Definition

A particular place serves as a person's or organization's main home, office, or center of operations.

Example

Valentina is based in Taipei but travels to Hong Kong every month for work.

based in [city] for a person's work location

The charity's main office is based at a small building near the university hospital.

based at [specific address/location]

Common collocations
  • based in London
  • based in the US
  • based at headquarters
  • based in a small town
Synonyms
  • stationed

    Used especially for military personnel or workers who are assigned to a specific location

  • situated

    More formal; describes the physical location of a building or organization

Grammar Patterns

based in [location]

based at [specific location/address]

Usage Note

Followed by 'in' for cities, countries, or regions, and by 'at' for specific addresses, buildings, or institutions. Cannot be used before a noun — 'a based-in-Tokyo firm' is incorrect; write 'a firm based in Tokyo'.

Common Mistakes

Our team is based at London.
Our team is based in London.
Use 'in' for cities and countries; use 'at' only for specific addresses or buildings.
She is a based-in-New-York journalist.
She is a journalist based in New York.
'Based in' cannot go before the noun.

3. Containing a particular substance or having a particular feature as a main or im

3.adjectiveB2
Definition

Containing a particular substance or having a particular feature as a main or important part.

Example

Many builders now prefer water-based paints because the smell is much lighter.

[noun]-based = made of / containing

The school uses a project-based learning method where students complete real tasks.

Common collocations
  • water-based paint
  • plant-based food
  • oil-based products
  • fact-based argument
  • class-based system
  • project-based learning
Synonyms

Grammar Patterns

[noun]-based

Usage Note

Typically used as a compound adjective placed before a noun, formed by adding '-based' to a noun. When placed before the noun, a hyphen is usually added (e.g., 'water-based paint', 'fact-based argument'). This sense can also appear after the noun with no hyphen: 'paints that are water based'.

Common Mistakes

A water based paint is easier to clean.
A water-based paint is easier to clean.
Add a hyphen when the compound adjective comes before the noun.
Oil based paints smell stronger.
Oil-based paints smell stronger.
Same rule: hyphenate before a noun.

Word family

Synonym discussion

Sense: adjective/1

These three phrases all describe the idea that something has a source or foundation, but they differ in how they are used. 'Based on' is the most general and common term — it works for ideas, decisions, stories, and systems of all kinds. 'Founded on' suggests a stronger, more deliberate act of building upon a principle (e.g., 'a society founded on equality') and is more common in formal or political writing. 'Derived from' focuses on the idea of something coming out of a source, such as a word origin ('the term is derived from Latin') or a chemical substance. 'Grounded in' implies a deep, solid connection to facts, experience, or evidence, and often carries a sense of reliability ('her theory is grounded in years of research'). Use 'based on' for everyday situations; reserve 'founded on' for abstract or institutional foundations, 'derived from' for origins and sources, and 'grounded in' for ideas backed by evidence.

founded onderived fromgrounded in

Common collocations

Adverbs

  • largely based
  • partly based
  • mainly based
  • primarily based
  • closely based

Phrases

  • based on the assumption that
  • based on the fact that
  • based in part on
  • based entirely on

Prepositions

Etymology

GreekLatinFrenchEnglish

The word 'based' comes from the verb 'base', which entered English from Old French 'baser' meaning 'to lay a foundation'. The French word came from Latin 'basis' ('foundation' or 'pedestal'), which was borrowed from Greek 'basis' ('a step, a base, a pedestal'). The participial adjective 'based' emerged in English to describe something that has a foundation or location, and over time developed the broader meanings of being derived from something or containing a certain substance.