define

Everyday

1. To say exactly what a word or idea means: «Can you define 'habitat'?» tree →
2. To state or show clearly what something is, its limits or its nature: «The rules define who can enter». tree →
3. To make the edges or shape of something clear and sharp: «a well-defined outline». tree →
4. To be the most important feature of someone or something: «Kindness defines her». tree →

In the lessons

In every subject, teachers ask pupils to «define» key words (define a prime number, define photosynthesis), and a glossary or dictionary gives definitions. In maths, we define shapes by their properties (a square is defined as a shape with four equal sides and four right angles). In computing, programmers «define» functions and variables. In PSHE: «Don't let one mistake define you». Phrases: «define a word», «clearly defined», «well-defined», «define yourself».

Examples

• Can you define the word «evaporate»? tree →
• A triangle is defined as a shape with three straight sides. tree →
• The river defines the border between the two countries. tree →
• The photo was sharp, with every leaf clearly defined. tree →
• In the program, we define a function called «jump». tree →
• Her courage defines her. tree →
• Don't let one bad test define you. tree →

Note

Noun: «definition». Adjective: «definite» (sure, fixed) and «definitive» (final, most complete) — easy to mix up. A good definition does not use the word itself inside it. In maths, definitions are exact; in everyday talk words can be looser.