grammar.nouns.plural-invariable
Nouns that don't change in the plural
Unstressed vowel + s stays put: el lunes / los lunes, la crisis / las crisis, el paraguas / los paraguas. Only the article marks number.
grammarA2v0.1.0
Explicación
Words ending in unstressed vowel + s are invariable: weekdays (el martes → los martes), Greek-derived -is words (la tesis, el análisis), and compounds like el cumpleaños, el abrelatas.
The article does the work: el lunes ('on Monday') vs los lunes ('on Mondays').
Ejemplos
Los lunes trabajo desde casa.
On Mondays I work from home.
On Mondays I work from home.
Región: global
Hubo varias crisis ese año.
There were several crises that year.
There were several crises that year.
Región: global