Birth Number

Definition: the root number of the date of birth. Depending on the school, it refers either to the full date (in which case the indicator coincides with the life path number) or to the day of the month only. Reducing birth dates to single digits is a foundational principle of numerology; the term in Russian-language practice overlaps with "birthday number."

[source: Numerology — Wikipedia (ru); the term is ambiguous, popular practice] Related: chislo-dnya-rozhdeniya, chislo-zhiznennogo-puti, kornevoe-chislo.