Meaning of QUANTUM in English

[quan.tum] n, pl quan.ta [L, neut. of quantus how much] (1567) 1 a: quantity, amount b: portion, part c: gross quantity: bulk

2. a: any of the very small increments or parcels into which many forms of energy are subdivided b: any of the small subdivisions of a quantized physical magnitude (as magnetic moment)

[2]quantum adj (1942): large, significant "a ~ improvement"

Merriam-Webster English vocab.      Английский словарь Merriam Webster.