Spanish Capitalization Rules That Trip Up English Speakers
Discover which Spanish words stay lowercase when English capitalizes them, plus the y/o conjunction swaps that trip up every learner.
Key phrases
Nos vemos el jueves en el mercado.
See you on Thursday at the market.
Mi cumpleaños es en octubre, no en diciembre.
My birthday is in October, not in December.
Mi vecino es alemán y habla español perfecto.
My neighbor is German and speaks perfect Spanish.
Nació en Alemania pero vive en Sevilla desde niño.
He was born in Germany but has lived in Seville since he was a child.
Mi tía es budista y medita cada mañana.
My aunt is Buddhist and meditates every morning.
Compramos fruta e higos frescos en el mercado.
We bought fruit and fresh figs at the market.
Necesitamos hierro y hielo para el experimento.
We need iron and ice for the experiment.
Se comunican por email e iMessage.
They communicate by email and iMessage.
¿Necesitas seis u ocho sillas para la mesa?
Do you need six or eight chairs for the table?
Llegan setenta u ochenta invitados a la boda.
Seventy or eighty guests are arriving at the wedding.
Necesito papel u hojas para imprimir el informe.
I need paper or sheets to print the report.
Capital Letters Play by Different Rules
Every language decides capitalization for itself, and Spanish makes some choices that feel backwards if you learned English first. The good news is the list of differences is short, and once you see the pattern, you’ll stop second-guessing yourself.
What Stays Lowercase
Several categories that English automatically capitalizes stay lowercase in Spanish:
- Days of the week — lunes, martes, jueves.
- Months of the year — enero, octubre, diciembre.
- Nationalities and languages — alemán, japonés, español (the person or the language, not the country).
- Religions and their followers — cristianismo, budista, musulmán.
If you’re used to writing “I speak Spanish on Mondays in October,” it can feel wrong to write it all lowercase in Spanish — but that’s exactly what natives do.
What Keeps Its Capital
Countries, cities, and proper names behave exactly like English: Alemania, Sevilla, Marruecos. The distinction is simple — the place name is capitalized, but the adjective describing someone’s nationality or the language they speak is not. Nació en Japón pero ya casi no habla japonés (He was born in Japan but barely speaks Japanese anymore) shows both rules in the same sentence.
When Y Turns Into E, and O Turns Into U
Spanish also swaps two conjunctions for purely acoustic reasons — nothing to do with capitals, but just as easy to get wrong in writing. Y (“and”) becomes e whenever the next word starts with an i or hi sound, so you don’t end up saying the same vowel twice back to back: fruta e higos, inglés e italiano. The swap doesn’t apply if that hi- leads into a diphthong instead of a plain i sound — hierro y hielo keeps its y because hie- doesn’t sound like a lone i.
The same logic flips o (“or”) into u before a word starting with o or ho: seis u ocho, papel u hojas. Unlike the y/e swap, this one has no exceptions — any o- or ho- sound triggers it, including every number built on ocho (80, 800, 8,000).
Pro Tip
Read your sentence out loud before you write the conjunction. If you catch yourself running two identical vowel sounds together, that’s your cue to swap y for e or o for u — your ear will catch it faster than any rule you memorize.
This lesson covers the conventions you’ll use daily — for the full picture of Spanish punctuation, capitalization, and mechanics, Sound Right, Write Right is the book that rounds out the series once you’ve got the social basics down.