noun
simple substance; elementary substance
Chemistry term: a substance consisting of atoms of a single element, as opposed to a compound.
酸素は単体として存在する。
Oxygen exists as a simple substance.
noun
standalone; separate item; solo item
General use: something that is alone, not part of a set or combination; often used in contrast to compound or combined items.
この部品は単体でも販売しています。
This part is also sold separately.
単体では効果が弱いが、組み合わせると強力だ。
It's weak on its own, but powerful when combined.