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Vertebrates and invertebrates.
You haven't stated any categories.
Elephant and OSTRICH
The two main categories are convenience goods and shopping goods; two lesser categories are specialty items and unsought goods.
Deoxyribose and Ribose
botany and zoology.
descriptive and inferential
IT is separated into two main categories (1) those which process information, such as computer systems, and (2) those which disseminate information, such as telecommunication systems.
animal and vegetable
linear and non-linear resistor
The two main categories of luster are metallic and non-metallic. Metallic luster appears shiny and reflective like metal, while non-metallic luster includes categories such as vitreous (glassy), pearly, greasy, and dull.
It is not possible to answer as there are many more than 2 categories.