How to express centuries in Spanish with Roman numerals

In Spanish, Roman numerals are always used to talk about centuries.

Learn how to talk about centuries in Spanish

The word for "century" in Spanish is "siglo". When we mention a certain century in Spanish we always use Roman numerals.

Note that is this section we are going to refer to cardinal and ordinal numbers. Examples of cardinal numbers are uno, dos, tres / one, two, three, examples of ordinal numbers are primero, segundo, tercero / first, second, third. If you need a handy way to remember the difference, think about cardinal numbers being used for counting and ordinal numbers being used for order.

In Spanish the first 10 centuries can be ordinal or cardinal

Roman numerals are primarily used as ordinal numbers but the common practice is that the first 10 centuries can be read as either ordinal or cardinal numbers. Let's look at some examples.

siglo I can be pronounced:

siglo VII can be pronounced:

siglo X can be pronounced:

In Spanish, centuries above 10 are cardinal numbers

However from the 11th century onwards, the centuries are read as cardinal numbers, not ordinal numbers. Let's look at some examples.

siglo XI is pronounced:

not "siglo décimo primero"

siglo XV is pronounced:

not "siglo décimo quinto"

siglo XXI is pronounced:

not "siglo vigésimo primero".

Here are some examples in context:

Using Roman Numerals

It's important to note that you must use Roman numerals to refer to centuries in Spanish. It is considered incorrect to write the century number in cardinal numbers using the Arabic numeric system (1, 2, 3, 4, 5, etc) or writing out the ordinal in letters (quince, dieciocho etc.). These examples are incorrect:

• Isaac Peral inventó el submarino en el siglo 15.
• Vivimos en el siglo 21.
• La reina Victoria murió a principios del siglo veinte, en 1901.

Also remember that the numeral goes after the word "siglo", not before. This is incorrect:

En el XXI siglo...

Using capital letters for the Roman numerals 

The Real Academia Española recommends that when referring to centuries you should write the Roman numerals in small capitals. For example: "siglo xxi" instead of using the regular size capital letters: "siglo XXI". However, you will find that in very many situations Roman numerals are often written using normal capital letters as we have done throughout this lesson because regular upper case letters are easier to implement.

More information about Roman numerals

If you need a reminder on how Roman numerals work, or to read about other circumstances where Spanish uses Roman numerals, see:

How to use Roman numerals in Spanish