Units of Time in Spanish

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Updated May 12, 2017

Need to know how to refer to a particular unit of time? Here are the most common ones in Spanish, listed from the shortest period of time to the longest:

el nanosegundo — nanosecond
el microsegundo — microsecond
el milisegundo — millisecond
el segundo — second
el minuto — minute
la hora — hour
el día — day
la semana, el septenario — week
la quincena — fortnight, two weeks (The term sometimes refers to a 15-day period or a half-month.)
el mes — month
el semestre — six months, half-year (The term can also refer to an academic semester.)
el año — year
el lustro — five years
el decenio, la década — 10 years, decade
el siglo — century
el milenio — millennium
el cron — million years
el eón — thousand million years, billion years in U.S. English (The term also can refer to an indefinitely long period of time.)

In addition, Spanish has a number of units of time that are seldom used, or are used in specific contexts. For example, bimestre and trimestre, are two-month and three-month periods, respectively, with similar month groupings possible. Similarly, bienio and septenio are two- and seven-year periods of time, respectively, with other groupings possible.