Οο

OMICRON

ὂ μικρόν · [o]

The 15th letter of the Greek alphabet.

MATHEMATICS

  • Asymptotic notation: o(n), o(1).
  • Small-o (strict order).

PROBABILITY

  • Appears in limits of sequences (o_p(1)).
  • In convergence in probability.

STATISTICS

  • Notation: o_p(1), O_p(·) in asymptotic theory.
  • Used in econometrics/estimation theory.

PRONUNCIATION

Ancient Greek
sound [o]
Modern Greek
όμικρον [ˈomikron] · sound [o]

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lowercase
uppercasesame as the Latin letter: LaTeX has no command for it

Note: notations vary between books/fields; these are the most common usages.