[ 'i:θə ]
■ noun
1》 (also diethyl ~ ) a pleasant-smelling, volatile, highly flammable liquid used as an anaesthetic and as a solvent.
2》 Chemistry any organic compound with an oxygen atom linking two alkyl groups.
3》 (also a~ ) chiefly literary the clear sky; the upper regions of air beyond the clouds.
4》 (also a~ ) Physics, historical a substance formerly postulated to permeate all space and to transmit light.
Derivatives
~ic i:'θɛrɪk , 'i:θ(ə)rɪk adjective
Origin
ME: from OFr., or via L. from Gk aithēr 'upper air', from the base of aithein 'burn, shine'.