不定元

bùdìngyuán
indeterminate element (math.), often denoted by x

CEDICT

math

Entry Composition

1 不定 bùdìng
  1. indefinite
  2. indeterminate
  3. (botany) adventitious
2 元 yuán
  1. currency unit (esp. Chinese yuan)
  2. (bound form) first; original; primary
  3. (bound form) basic; fundamental
  4. (bound form) constituent; part
  5. (prefix) meta-
  6. (math.) argument; variable
  7. era (of a reign)
  8. (Tw) (geology) eon