The quality or state of being gaseous or having the nature of gas; the tendency to form or exist as gas.
From gaseous plus the abstract noun suffix -ity, creating a formal scientific term. Related to gaseity but formed through slightly different Latin morphology.
English has both 'gaseity' and 'gaseosity' for the same concept—sometimes scientists couldn't decide which suffix sounded best, so they created competing versions. Language evolves through competitive variation!
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