Union
$$A \cup B =$$
{ earth, fire, importance, informative, interest, metal, need to know, relevance, right to know, timeliness, water, wood }
Symmetric Difference
$$A \ominus B =$$
{ earth, fire, importance, informative, interest, metal, need to know, relevance, right to know, timeliness, water, wood }
Cartesian Product
$$A \times B =$$
{ (importance, earth),
(importance, fire),
(importance, metal),
(importance, water),
(importance, wood),
(informative, earth),
(informative, fire),
(informative, metal),
(informative, water),
(informative, wood),
(interest, earth),
(interest, fire),
(interest, metal),
(interest, water),
(interest, wood),
(need to know, earth),
(need to know, fire),
(need to know, metal),
(need to know, water),
(need to know, wood),
(relevance, earth),
(relevance, fire),
(relevance, metal),
(relevance, water),
(relevance, wood),
(right to know, earth),
(right to know, fire),
(right to know, metal),
(right to know, water),
(right to know, wood),
(timeliness, earth),
(timeliness, fire),
(timeliness, metal),
(timeliness, water),
(timeliness, wood) }
Wu Xing