Days of the Week in Spanish
Lunes, martes, miércoles, jueves, viernes, sábado, domingo. Learning the seven words is quick. The part that trips people up is the plural: to say "on Mondays" you change el to los — but five of the seven words themselves never change, so los lunes looks singular. Flip the toggle below and watch which two actually move.
The plural that isn't there
Five of the seven days — lunes, martes, miércoles, jueves, viernes — already end in -s, and Spanish leaves them untouched in the plural. So the singular and plural look identical, and the only thing that signals "every week" is the article: el lunes is one specific Monday, los lunes is Mondays in general. Just two days break the run: sábado and domingo don't end in -s, so they pluralise normally — los sábados, los domingos. Get those two right and you've got the whole system.
No "on", and no capital letters
Spanish has no word for "on" with days. "I work on Monday" is simply trabajo el lunes, and "I work on Mondays" is trabajo los lunes — the article does all the work. Days are also never capitalised mid-sentence: it's lunes, not Lunes, unless it opens the sentence. All seven are masculine, which is why the article is always el or los, never la.
Two accents, and the Roman gods underneath
Only two days carry a written accent — miércoles and sábado — and it isn't decorative: it marks the stressed syllable, so dropping it is a spelling error. As for where the names come from, Spanish inherited the same Roman planet-day scheme as French: lunes from the Moon, martes from Mars, miércoles from Mercury, jueves from Jupiter, viernes from Venus, with sábado(Sabbath) and domingo (the Lord's day) Christianised at the weekend. The full planet-god story — and why English kept the Norse gods instead — is laid out on days of the week in French.
Quick quiz — does it take an -s?
Seven questions, all on the rule that catches people: which days add the plural -s, and which don't.
“on Thursdays” — every week
Pick the correct Spanish form.
Frequently asked questions
Why does "los lunes" look the same as "lunes"?
Because lunes is invariable — it already ends in -s, so it never changes for the plural. The only thing that shows the plural is the article: el lunes (one Monday) versus los lunes (Mondays).
Which Spanish days add an -s in the plural?
Only two: sábado → sábados and domingo → domingos. The other five (lunes, martes, miércoles, jueves, viernes) keep exactly the same spelling.
How do you say "on Mondays" in Spanish?
Los lunes. Spanish uses no word for "on" — the plural article los carries the "every week" meaning. For a single coming Monday, use el lunes.
Are days of the week capitalised in Spanish?
No — only at the start of a sentence. You write "trabajo el lunes", not "el Lunes".
Which days carry a written accent?
Two: miércoles and sábado. The accent marks the stressed syllable and is not optional.
- Real Academia Española (RAE) — rule that days ending in -s are invariable in the plural; lowercase convention for days.
- RAE — written-accent rules placing the stress mark on miércoles and sábado.
- Latin planetary-day origins: lunae/Martis/Mercurii/Jovis/Veneris dies, plus sabbatum and dies Dominica for the weekend.
- ISO-8601 — Monday as the first day of the week, as used in Spain.
Seven days, but only two of them have a plural you can see — the rest hide it in a single small word: los.