The days of the week in Spanish
lunes - Monday
martes - Tuesday
miércoles - Wednesday
jueves - Thursday
viernes - Friday
sábado - Saturday
domingo - Sunday
el fin de semana - the weekend
In Spanish, days of the week are not capitalized: lunes, martes, etc. All of them are masculine. In order to make them plural, we just use the plural article (el martes, los martes), except for sábado and domingo: el sábado, los sábados; el domingo, los domingos.
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