define + object + as + noun
Classifying or identifying
Use as to say what something is considered or described as.
The report defines poverty as lack of basic resources.
Define by, define as or define in?
Define as is the standard pattern for classification. Define by is used for features or methods. Define in appears when referring to language or terms used.
Quick answer
How do define as, define by, and define in differ?
Use define as to classify something: The law defines theft as a crime. Use define by for characteristics: Success is defined by hard work. Use define in when talking about wording or language.
The policy defines remote work as flexible employment.
Great leadership is often defined by empathy.
The term is defined in simple language.
Great leadership is often defined by empathy.
The term is defined in simple language.
Choose the pattern by meaning
These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.
define by + feature
Describing distinguishing qualities
Use by to mention the characteristic used to identify something.
The genre is defined by strong rhythms.
define in + language/terms
Explaining wording or style
Use in when referring to the language, terms, or way a definition is expressed.
The concept is defined in legal terms.
See the difference in context
The same subject can take different constructions because each sentence answers a different question.
Construction
Example
Meaning
define as + category
Scientists define water as a compound.
Standard classification structure.
defined by + feature
Her style is defined by simplicity.
Shows a characteristic or basis.
defined in + terms/language
The rule is defined in plain English.
Refers to wording or medium.
Common mistakes
Some combinations appear in real text but do not mean what learners often assume.
Using define by for classification
Use define as when naming a category or identity.
✕ The law defines fraud by a criminal offence. ✓ The law defines fraud as a criminal offence.Using define in for characteristics
Use by when talking about defining features.
✕ The movement is defined in bold colours. ✓ The movement is defined by bold colours.Quick practice
Choose the expression that matches the intended meaning.
1. The contract defines negligence ___ failure to take reasonable care.
2. The brand is defined ___ minimal design.
3. The procedure is defined ___ technical terms.
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Frequently asked questions
Is define as the most common structure?
Yes. It is the standard way to classify or identify something.
What does defined by mean?
It means identified or characterised through a quality, feature, or factor.
Can define in describe language?
Yes. Use it when discussing the terms or wording of a definition.
Related preposition guides
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