This brief article explains the logic of the Spanish number system. It shows how to express any number orally and in writing, including decimals.

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### Numbers in Spanish

The Spanish number system is quite simple once you grasp its logic. The first step is to get an overview of the system. The numbers 1-15 have unique names. The numbers from 16 to infinity are formed by a number expressed as a multiple of ten and adding a number from 1-9, connecting them with

, which means and. Usually, for numbers expressed as 16-29, the resulting number is spelled as one word and the**y**is changed to an**y**. From 31-99, they are written as separate words and**i**is used.**y**Thus, learning the numbers from 1-15 as a group is a very important first step, followed by the numbers 16-19, then 20, 21 and 22. The next step is to learn the names of the rest of the multiples of tens or the decades from 30-90. Thus the first step consists of the following:

- cero – 0
- uno – 1
- dos – 2
- tres – 3
- cuatro – 4
- cinco – 5
- seis – 6
- siete – 7
- ocho – 8
- nueve – 9
- diez – 10
- once – 11
- doce – 12
- trece – 13
- catorce – 14
- quince – 15

The next step contains the rest of the teens and also shows the way to add a number to the decade. Note that the

is changed to an**y**when writing the names of these numbers.**i**- dieciseis – 16
- diecisiete – 17
- dieciocho – 18
- diecinueve – 19

From this point on, the same logic of adding a number from 1-9 to the decade is used:

- veinte – 20
- veintiuno – 21
- veintidos – 22

Next, learn the numbers by tens. Notice that with the notable exceptions of 50, 70 and 90, all the names are built directly on the numbers 2-9:

- veinte – 20
- treinta – 30
- cuarenta – 40
- cincuenta – 50
- sesenta – 60
- setenta – 70
- ochenta – 80
- noventa – 90

Remember that 31 is

,**treinta y uno***not*. The same applies for the rest of the numbers to 99.**treintaiuno**Lastly, 100 is simply

, but 101 is**cien**. When writing numbers from any one of the hundreds plus 9, the names of the individual numbers are separated and so**ciento y uno**is used instead of**y**. Counting by hundreds, you’ll notice that they are written as one word and also that 500, 700 and 900 are slightly irregular, just as 50, 70 and 90 are:**i**- cien – 100
- doscientos – 200
- trescientos – 300
- cuatrocientos – 400
- quinientos – 500
- seiscientos – 600
- setecientos – 700
- ochocientos – 800
- novecientos – 900

One thousand is

. An easy way for some people to remember that is to recall that**mil****M**is the Roman numeral for a thousand.is an interesting word in that**Mil**or**un**are never used before it as we use one or an with thousand when saying, for instance**una**. In Spanish, it is simply**I own a thousand books**. From this point on, the numbers are all built using the same logic as English and the names of the large numbers are almost the same, with a notable point of international confusion surrounding what a billion is. In many parts of Latin America, the billons follow the millions and one billion is un billón and two billion are dos billones. But is some places, a billion is called mil millones and billion becomes the trillions. A similar usage difference occurs between British and American English.Here are some examples of large numbers and how they would be expressed:**Tengo mil libros**2,652,543: dos millones, seiscientos cincuenta y tres mil, quinientos cuarenta y tres.

432,785,345,102: cuatro cientos treinta y dos billones (or mil millones), setecientos ochenta y cinco millones, trescientos cuarenta y cinco mil, ciento y dos.

A decimal is expressed as either

(**punto***period*) or as(**coma***comma*), the usage varying from country to country. In other words, the usage of these two symbols may be exactly the reverse of what we do in the USA.4.52: cuatro punto cincuenta y dos or, if written 4,52: cuatro coma cincuenta y dos.

One very good way to practice numbers is to count things. Paper clips, shirts, whatever you're counting. One way to rapidly review the number vocabulary and the way in which the y is used between ones and tens columns is to count from 1-21, then say 22 and begin counting by 11's to 99. Then say 100, 101, 111 and begin counting by 111's to 999. This will cover all the vocabulary and formats necessary for expressing numbers.

### References

- Author's more than 20 years experience teaching and translating Spanish.