noun
empty set
Mathematical term for the set containing no elements, often denoted by ∅ or { }.
空集合は任意の集合の部分集合である。
The empty set is a subset of any set.
空集合 is a specific type of 集合 (set), namely the one with no elements.
Compound of 空 (empty) and 集合 (set), a direct translation of the English mathematical term 'empty set'.