Union
$$A \cup B =$$
{ becoming, being, cause, effect, enclosure, essence, existence, hearth, life, many, mechanism, mound, one, roof, universal }
Symmetric Difference
$$A \ominus B =$$
{ becoming, being, cause, effect, enclosure, essence, existence, hearth, life, many, mechanism, mound, one, roof, universal }
Cartesian Product
$$A \times B =$$
{ (becoming, enclosure),
(becoming, hearth),
(becoming, mound),
(becoming, roof),
(being, enclosure),
(being, hearth),
(being, mound),
(being, roof),
(cause, enclosure),
(cause, hearth),
(cause, mound),
(cause, roof),
(effect, enclosure),
(effect, hearth),
(effect, mound),
(effect, roof),
(essence, enclosure),
(essence, hearth),
(essence, mound),
(essence, roof),
(existence, enclosure),
(existence, hearth),
(existence, mound),
(existence, roof),
(life, enclosure),
(life, hearth),
(life, mound),
(life, roof),
(many, enclosure),
(many, hearth),
(many, mound),
(many, roof),
(mechanism, enclosure),
(mechanism, hearth),
(mechanism, mound),
(mechanism, roof),
(one, enclosure),
(one, hearth),
(one, mound),
(one, roof),
(universal, enclosure),
(universal, hearth),
(universal, mound),
(universal, roof) }
The Four Elements of Architecture