Look up first-order in Wiktionary, the free dictionary.
In mathematics and other formal sciences, first-order or first order most often means either:
- "linear" (a polynomial of degree at most one), as in first-order approximation and other calculus uses, where it is contrasted with "polynomials of higher degree", or
- "without self-reference", as in first-order logic and other logic uses, where it is contrasted with "allowing some self-reference" (higher-order logic)
In detail, it may refer to: