一次

yīcì
  1. first
  2. first time
  3. once
  4. (math.) linear (of degree one)

CEDICT

math

Entry Composition

1 一 yī
  1. one
  2. single
  3. a (article)
  4. as soon as
  5. entire; whole; all; throughout
  6. "one" radical in Chinese characters (Kangxi radical 1)
  7. also pr. yāo for greater clarity when spelling out numbers digit by digit
2 次 cì
  1. next in sequence
  2. second
  3. the second (day, time etc)
  4. secondary
  5. vice-
  6. sub-
  7. infra-
  8. inferior quality
  9. substandard
  10. order
  11. sequence
  12. hypo- (chemistry)
  13. classifier for enumerated events: time