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primary quality

/ˈpraɪˌmɛri ˈkwɒlɪti/ · pri·ma·ry qual·i·ty
noun
  1. In philosophy, a property of an object that exists independently of any observer, such as shape, size, motion, or number. Locke argued that a sphere’s roundness is a primary quality, whereas its color is a secondary quality.
  2. A fundamental or essential attribute of something. Reliability is considered a primary quality of a good scientific instrument.
Did you know? Locke’s distinction between primary and secondary qualities laid the groundwork for later debates in physics about whether space, time, and mass are mind‑independent realities.
Written by Lexi Wordsworth, Dictionary Editor 0 lookups Added Jul 29, 2026