icosahedron
C2Technical / Academic
Definition
Meaning
A three-dimensional geometric shape with twenty flat polygonal faces.
In geometry, a regular icosahedron is one of the five Platonic solids, composed of twenty equilateral triangular faces. In broader contexts, it can refer to any polyhedron with twenty faces, which may vary in shape.
Linguistics
Semantic Notes
The term is almost exclusively used in mathematical, scientific, gaming (e.g., dice), and architectural contexts. It is a hypernym; specific types include 'regular icosahedron' and 'truncated icosahedron' (e.g., a football/soccer ball pattern).
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning or usage. Pronunciation differs slightly (see IPA).
Connotations
Identical technical connotations in both varieties.
Frequency
Equally rare in general discourse in both regions, confined to specialised fields.
Vocabulary
Collocations
Grammar
Valency Patterns
The [material] icosahedron [verb, e.g., *has*, *contains*] twenty faces.An icosahedron is a type of [noun, e.g., *polyhedron*, *solid*].Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “[No established idioms for this technical term]”
Usage
Context Usage
Business
Virtually never used.
Academic
Used in mathematics, geometry, chemistry (viral capsids, e.g., adenovirus), and physics.
Everyday
Extremely rare; might appear in puzzles, advanced board games, or educational contexts.
Technical
Primary domain. Used in geometry, 3D modelling, crystallography, and molecular design.
Examples
By Part of Speech
verb
British English
- [No standard verb form]
American English
- [No standard verb form]
adverb
British English
- [No standard adverb form]
American English
- [No standard adverb form]
adjective
British English
- The viral capsid has an icosahedral symmetry.
- They studied icosahedral structures in geometry.
American English
- The protein forms an icosahedral shell.
- Icosahedral designs are common in geodesic domes.
Examples
By CEFR Level
- A football has a shape like an icosahedron.
- In maths class, we learned about a shape called an icosahedron.
- The regular icosahedron is one of the five Platonic solids, with twenty triangular faces.
- Many viruses, such as the adenovirus, exhibit an icosahedral capsid structure due to its geometric efficiency.
Learning
Memory Aids
Mnemonic
Think: 'I COuld SAy HE DRENched' – but it has 20 faces. 'Icosa' sounds like 'eye-coat-sa', and 'hedron' relates to 'face' (like polyhedron). Remember: An ICOSAhedron has twenty faces, like an ICOSAgon has twenty sides.
Conceptual Metaphor
STRUCTURE AS GEOMETRY (e.g., 'The virus has an icosahedral shell' implies a highly ordered, efficient, and stable structure).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Direct calque 'икосаэдр' is correct and identical in meaning. No false friends. Ensure stress is on the correct syllable in pronunciation (e.g., икосАэдр).
Common Mistakes
- Misspelling: 'icosohedron', 'icosahedran'.
- Mispronunciation: placing stress on the wrong syllable (e.g., /aɪˈkɒs.ə/).
- Confusing with dodecahedron (12 faces).
Practice
Quiz
Which of the following is a defining property of a regular icosahedron?
FAQ
Frequently Asked Questions
An icosahedron has twenty faces.
A standard d20 die is a regular icosahedron, meaning all its faces are identical equilateral triangles.
It is primarily used in geometry, chemistry (for molecular structures), virology, and in the context of dice for tabletop games.
An icosahedron is a specific type of polyhedron (a 3D shape with flat faces). 'Polyhedron' is the general term; an icosahedron is a polyhedron with exactly twenty faces.