element
n. countablen. a basic part of something bigger. It can also mean one of the simple substances, like oxygen or gold, that everything in the world is made of.
n. a fundamental part or constituent of a larger whole; in chemistry, a substance consisting of atoms which all have the same number of protons.
Trust is a key element of a good friendship.
The detective noticed a strange element in the witness's story that didn't match the evidence.
While the plot is engaging, the most compelling element of the novel is the author's ability to evoke the atmosphere of nineteenth-century London through sensory detail.
From Middle English element, from Old French element, from Latin elementum (“a first principle, element, rudiment”) (see further etymology there). The verb is from Middle English elementen, from the noun.
Often used with the preposition 'of' to describe a component part.