You're standing at a busy deli in Madrid or maybe just trying to give your phone number to a new friend in Mexico City, and suddenly, your brain freezes. It’s the simplest number. The first one we usually learn. But for some reason, the way to spell 0 in Spanish feels like a trick question the second you have to write it down or say it out loud.
Is it a 'c' or an 's'? Does it have an accent?
Honestly, it’s cero.
Just four letters. C-E-R-O. It sounds a bit like the English word "zero," but you’ve got to swap that buzzing 'z' for a crisp, Spanish 'c' or a soft 's' sound depending on where you are in the world. It’s one of those foundational words that seems easy until you realize it behaves a little differently than other numbers in the Spanish language.
Why Cero is Different from Other Numbers
Most people start their Spanish journey with uno, dos, tres. By the time they get to ten, they feel like experts. But cero is the lonely outlier. Unlike the number one (uno), which changes to un or una depending on the gender of the noun it’s hugging, cero is a bit of a stickler for the rules.
It doesn't change.
If you have zero shirts, it’s cero camisas. If you have zero dollars, it’s cero dólares. It stays masculine and singular in its spelling, even if the thing you have "none" of is feminine or plural. It’s a constant. It’s reliable.
But here is where it gets kind of weird for English speakers. In English, we use "zero" for everything—temperatures, sports scores, phone numbers, and even the year 2005 ("two-thousand and oh-five"). In Spanish, cero doesn't always get the invite to the party.
How to Spell 0 in Spanish and When to Use It
If you are writing a formal check or an academic paper, you spell it cero. No exceptions. But if you are watching a soccer match—excuse me, fútbol—and the score is 0-0, the announcer probably won't scream "cero a cero" with much enthusiasm. They might, but it’s just as likely they’ll use other terms.
In tennis, for example, the score of zero is often referred to as nada. If you're talking about a score of 2-0, a Spaniard might say dos a cero, but they might also just say dos a nada.
Then there is the phone number issue.
In many parts of the Spanish-speaking world, you don't say "oh" like we do in English. If your number has a 0 in it, you say cero. You have to. If you try to say the letter "o" (oh), people are going to look at you like you’ve got two heads. It just doesn’t compute.
Regional Pronunciation Quirks
While the spelling remains cero across the globe, the way it hits the ear changes the moment you cross an ocean.
In Spain, specifically in central and northern parts of the country, they use what linguists call distinción. This means the 'c' in cero is pronounced like the 'th' in "think." It’s a sharp, lisped sound: th-er-oh.
If you hop on a flight to Buenos Aires, Bogotá, or Mexico City, that disappears. There, you’ll hear seseo. The 'c' sounds exactly like an 's'. It’s seh-roh.
Neither is "more correct" than the other. It’s just flavor. But if you’re trying to spell 0 in Spanish correctly, don’t let the 'th' sound in Spain trick you into thinking there’s a 'z' or a 'th' in the spelling. It’s always a 'c'.
The Confusion with "Null" and "None"
Sometimes, cero isn't the word you want at all.
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Think about the phrase "zero tolerance." In Spanish, that’s tolerancia cero. It follows the noun. But what about when a scientist talks about "absolute zero"? That’s cero absoluto.
There’s also the concept of "nil" or "nothing." In some contexts, especially in legal or highly technical documents, you might see the word nulo. While nulo means null or void, it’s conceptually linked to zero. However, if you are filling out a form and need to write the number 0 as a word, stick to cero.
Common Spelling Mistakes to Avoid
Even though it’s only four letters, people still find ways to mess it up. Here are the most common traps:
- Sero: This is usually a phonetic mistake made by learners in Latin America who hear the 's' sound and assume that’s how it’s written. It's wrong.
- Zero: This is the "English brain" taking over. In Spanish, the letter 'z' is almost never followed by an 'e' or an 'i'. If you see a 'z' before an 'e', it’s usually a loanword or a very rare exception.
- Ceero: Adding an extra 'e' to try and mimic the long 'e' sound in English "zero." Spanish vowels are short and clipped. Eh, not eee.
Mathematics and Decimals
When you get into the weeds of math, cero becomes even more prominent.
In English, we say "zero point five" (0.5). In many Spanish-speaking countries, they use a comma instead of a period for decimals. So, 0,5 is written out as cero coma cinco.
It’s a small detail, but if you’re working in finance or science, it’s a massive distinction. Using a point instead of a comma can lead to genuine confusion in international business transactions. If you’re writing it out: cero coma cinco.
The Cultural Weight of Zero
Language is more than just grammar. It’s how we perceive the world.
In Spanish, there’s a common slang phrase: ser un cero a la izquierda.
Literally, it means "to be a zero to the left." Think about it. If you put a zero to the left of a number (01), it doesn't change the value. It’s useless. So, if someone tells you that you are a cero a la izquierda, they are basically saying you’re a nobody or that your opinion doesn’t count in this specific situation.
Ouch.
It’s a vivid way that the spelling and placement of 0 in Spanish makes its way into everyday insults and observations.
Why Getting the Spelling Right Matters
You might think, "It’s just a zero, who cares?"
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But spelling cero correctly is a sign of respect for the language's internal logic. Spanish is a very phonetic language. Once you learn the rules, there are very few surprises. The 'c' followed by an 'e' always makes that 's' or 'th' sound. Knowing that cero starts with a 'c' reinforces your understanding of how thousands of other words—like cerveza, cielo, and cena—are constructed.
Actionable Steps for Mastering Spanish Numbers
If you want to move beyond just knowing how to spell 0 in Spanish, you need to integrate it into your daily flow.
- Practice with phone numbers: Write down five phone numbers and say them out loud in Spanish. Every time you hit a 0, say cero. Don't skip it.
- Watch the weather: Spanish weather reports are great for this. You’ll hear "cero grados" (zero degrees) frequently if you're looking at mountain regions or winter forecasts.
- Write it, don't just type it: Muscle memory is real. Grab a pen and write cero ten times. It sounds silly, but it kills the urge to write "zero" with a 'z'.
- Check your decimals: If you are traveling to Spain or South America, practice writing prices. Instead of $0.50, try writing 0,50€ and saying cero con cincuenta.
The beauty of the Spanish language is its consistency. Once you’ve nailed down the fact that it’s cero with a 'c', you’ve unlocked a small but vital piece of the linguistic puzzle. It’s a tiny word, but using it correctly makes you sound less like a tourist and more like someone who actually understands the rhythm of the tongue.
Don't overthink it. It's just cero. Keep it simple, keep it crisp, and remember that in Spanish, the letter 'c' is your best friend when 'e' follows behind.