10U

10u is a designation used to indicate an age category in youth sports. The "U" stands for "Under," so 10u refers to players who are under the age limit at a specified cutoff date. The term is common in leagues and tournaments for baseball and softball and is also used in other sports such as soccer, basketball, and lacrosse. The exact cutoff varies by league and country and is typically based on a player's age on a specific date; some leagues allow players who turn the limit during the season to remain eligible. The designation is frequently seen as 10U or 10u, with the capitalization depending on the governing body.

In practice, 10u divisions emphasize skill development and participation. Games and rules are often adjusted to accommodate younger players, with formats like coach-pitch or machine-pitch in baseball and softball and simplified rules to encourage fundamentals. Competitive structures, postseason tournaments, and progression paths usually align with a league’s broader age-group framework, linking to higher divisions such as 12U or 14U as players age.

In other contexts, "10u" may appear in technical notation as shorthand, where the "u" represents the micro- prefix (μ) in ASCII text. For example, "10uF" is read as ten microfarads. However, "10u" without a unit can be ambiguous and is not standard SI notation; official notation uses the μ symbol or explicit units with prefixes (for example, μF, μH).