In geometry, the adjective diametrical has to do with a straight line running through the middle of a circle — all diametrical lines will intersect at the very center.

Aside from its mathematical meaning, you an also use this word to emphasize how opposed two things (or people) are. If you and your sister couldn't possibly be more different (she's a morning person, while you're a night owl; she's outgoing, you're an introvert), you can say you're diametrical opposites. The root of diametrical is the Greek diametros, "diagonal of a circle."

Definitions of diametrical

adj related to or along a diameter

diametral, diametric

adj characterized by opposite extremes; completely opposed

diametrical (or opposite) points of view”
diametric, opposite, polar
unlike in nature, quality, form, or degree

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