Is eighteen the legal age of adulthood in Spanish-speaking countries?

In most Spanish-speaking countries, dieciocho años marks the legal age of majority, granting the right to vote, sign contracts, and purchase alcohol in many jurisdictions.

How do you say eighteenth in Spanish?

The ordinal form is decimoctavo (masculine) or decimoctava (feminine). However, in everyday speech, many people say el dieciocho or número dieciocho instead of the formal ordinal.

Why is dieciocho written as one word?

Spanish merged the teens (16–19) into single words during spelling reforms. Dieciocho comes from diez y ocho but is now always written together, following the same pattern as dieciséis and diecisiete.

Spanish vocabulary · Beginner

How to Say 18 in Spanish: Dieciocho

Written by Sofia Ramirez, Lead Spanish Curriculum Editor · Reviewed May 2026

Dieciocho · number / adjective · dyeh-see-OH-choh

Dieciocho is the Spanish word for the number eighteen. Like all Spanish numbers from sixteen to nineteen, it is written as one word, combining diez (ten) and ocho (eight) into a single term.

dyeh-see-OH-choh

Mi hermana cumple dieciocho años mañana.

My sister turns eighteen tomorrow.

18 in Spanish: Quick Reference

Below are the most common Spanish words for 18, with pronunciation and regional usage notes.

Spanish	English	Pronunciation	Region / Register
dieciocho	18	dyeh-see-OH-choh	Default, widely understood
decimoctavo/decimoctava	18		universal (ordinal: eighteenth)

How Native Speakers Use Dieciocho

Real example sentences across three contexts you'll actually run into.

Age and milestones

Cuando cumplí dieciocho años, mis padres me regalaron un viaje.

When I turned eighteen, my parents gave me a trip as a gift.

Turning eighteen is significant in many Spanish-speaking countries as the legal age of adulthood.

Telling time

Son las dieciocho horas en horario militar.

It is eighteen hundred hours in military time.

In formal or 24-hour time, dieciocho corresponds to 6 p.m.

Counting items

Hay dieciocho estudiantes en la clase de español.

There are eighteen students in the Spanish class.

Using dieciocho as a simple quantity.

Avoid These Mistakes When Using Dieciocho

Splitting it into two words

Incorrect: diez y ocho

Correct: dieciocho

Dieciocho is always spelled as one word in contemporary Spanish. The historical form diez y ocho survives in some old texts, but modern orthography merged it into a single unit with an accent-free spelling.

Misspelling with a double c

Incorrect: dieciochio

Correct: dieciocho

The ending comes from ocho, not ochio. Keep the spelling identical to the standalone number ocho.

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See Dieciocho used by native speakers

Parrot's short-form videos feature native speakers using dieciocho in real situations. Context-based exposure beats flashcards, you hear Mi hermana cumple dieciocho años mañana. while watching someone live the moment, connecting meaning, sound, and rhythm at once.

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Common Questions About 18 in Spanish

Is eighteen the legal age of adulthood in Spanish-speaking countries?: In most Spanish-speaking countries, dieciocho años marks the legal age of majority, granting the right to vote, sign contracts, and purchase alcohol in many jurisdictions.
How do you say eighteenth in Spanish?: The ordinal form is decimoctavo (masculine) or decimoctava (feminine). However, in everyday speech, many people say el dieciocho or número dieciocho instead of the formal ordinal.
Why is dieciocho written as one word?: Spanish merged the teens (16–19) into single words during spelling reforms. Dieciocho comes from diez y ocho but is now always written together, following the same pattern as dieciséis and diecisiete.