Definition of allotropy in US English:

allotropy

noun

Chemistry
  • The existence of two or more different physical forms of a chemical element.

    • ‘With the exception of nitrogen, all group V elements show allotropy.’
    • ‘The best known example for allotropy is iron.’
    • ‘The difference in the arrangement of space in the atoms that make up the structure of an element is called allotropy.’
    • ‘An example of allotropy is carbon, which can exist as diamond, graphite, and amorphous carbon.’

Origin

Mid 19th century: from Greek allotropos ‘of another form’, from allo- ‘other’ + tropos ‘manner’ (from trepein ‘to turn’).

Pronunciation

allotropy

/əˈlätrəpē/