■ noun
1》 the smallest particle of a chemical element, consisting of a positively charged nucleus (containing protons and typically also neutrons) surrounded by negatively charged electrons.
2》 [usu. with negative ] an extremely small amount.
Origin
C15: from OFr. ~e , via L. from Gk ~os 'indivisible', based on a- 'not' + temnein 'to cut'.