/ ˈkwɒntəm; NAmE ˈkwɑːn-/ noun
( pl. quanta / -tə; NAmE /) ( physics ) a very small quantity of electromagnetic energy
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WORD ORIGIN
mid 16th cent. (in the general sense quantity ): from Latin , neuter of quantus how great, how much. The current sense dates from the early 20th cent.