Union
$$A \cup B =$$
{ Biochemistry, Biology/Microbiology, Botany, Chemistry, Earth Science/Life Science, Ecology, Geology, Meteorology, Oceanography, Physics/Cosmology, Space Science, Zoology, interval, nominal, ordinal, ratio }
Symmetric Difference
$$A \ominus B =$$
{ Biochemistry, Biology/Microbiology, Botany, Chemistry, Earth Science/Life Science, Ecology, Geology, Meteorology, Oceanography, Physics/Cosmology, Space Science, Zoology, interval, nominal, ordinal, ratio }
Cartesian Product
$$A \times B =$$
{ (interval, Biochemistry),
(interval, Biology/Microbiology),
(interval, Botany),
(interval, Chemistry),
(interval, Earth Science/Life Science),
(interval, Ecology),
(interval, Geology),
(interval, Meteorology),
(interval, Oceanography),
(interval, Physics/Cosmology),
(interval, Space Science),
(interval, Zoology),
(nominal, Biochemistry),
(nominal, Biology/Microbiology),
(nominal, Botany),
(nominal, Chemistry),
(nominal, Earth Science/Life Science),
(nominal, Ecology),
(nominal, Geology),
(nominal, Meteorology),
(nominal, Oceanography),
(nominal, Physics/Cosmology),
(nominal, Space Science),
(nominal, Zoology),
(ordinal, Biochemistry),
(ordinal, Biology/Microbiology),
(ordinal, Botany),
(ordinal, Chemistry),
(ordinal, Earth Science/Life Science),
(ordinal, Ecology),
(ordinal, Geology),
(ordinal, Meteorology),
(ordinal, Oceanography),
(ordinal, Physics/Cosmology),
(ordinal, Space Science),
(ordinal, Zoology),
(ratio, Biochemistry),
(ratio, Biology/Microbiology),
(ratio, Botany),
(ratio, Chemistry),
(ratio, Earth Science/Life Science),
(ratio, Ecology),
(ratio, Geology),
(ratio, Meteorology),
(ratio, Oceanography),
(ratio, Physics/Cosmology),
(ratio, Space Science),
(ratio, Zoology) }
Level of measurement