We explain what ordinal numbers are, how to write them, and their differences with cardinal numbers. Also, ordinal numbers from 1 to 1000.
What are ordinal numbers?
In mathematics, ordinal numbers are those that, instead of indicating the quantity of things to which one refers, indicate the order of things within a given sequence or succession. That is, they are the numbers with which we express the order or sequence of things, rather than their quantity.
For example, given any three elements in a sequence 1, 2, 3, we will say that 1 is the first element, 2 is the second and three is the third. These are, precisely, their ordinals, and they are differentiated from the cardinal numbers, with which quantities are expressed in a common way. You must read about Polygon once.
Ordinal numbers have their correlate in the language in ordinal adjectives. As such, they are endowed with gender and number, and are usually used in common language up to the tenth (10) or twelfth (12), since from there they become more complicated. It is normal for ordinals above that point to be replaced with cardinal numbers (thus, John XXIII can be said “John twenty-three” instead of “John twenty-third”).
Difference between ordinal numbers and cardinal numbers
Cardinal numbers are natural numbers that are used to express a quantity, that is, a certain number of things. For example, when we say that we have five fingers on each hand, we are enumerating them and, therefore, using cardinal numbers to express the total number of fingers counted: five (5) on each hand, ten (10) in total.
However, when it comes to ordering the fingers of the hand and counting them from the thumb to the little finger, we are no longer so concerned with how many there are, but rather in what order they are found. Thus, we can say that the thumb is the first (1st), the index finger is the second (2nd), the middle finger is the third (3rd), the ring finger is the fourth (4th) and the little finger is the fifth (5th), and for this we have used ordinal numbers, since they are used to express order and sequence, instead of total quantity. Maybe you should definitely read about Square Meter once.
How are ordinal numbers written?
Ordinal numbers are written using a sign that accompanies them and distinguishes them from cardinal numbers: the degree sign (°). Thus, for example, the number one (1) becomes the first (1°). It is possible that this symbol is replaced by a superscript letter “a” (a) when it is necessary to distinguish the feminine gender of the referent: first (1a).
On the other hand, the names of ordinal numbers are formed through the use of specific suffixes, which serve to express a notion of a certain quantity. These suffixes changed a lot throughout the history of the language and that is why they may seem strange to us today. The main suffixes are:
- ero/era, used in the first of the ordinals, as in first (1°) or third (3°).
- to/ta, the most common of the suffixes among the ordinals, as in fifth (5°) or sixth (6°).
- eno/ena, incorporated in medieval Spanish but lost except in the case of noveno (9°).
- avo/ava, used only for fractional numbers. For example: un catorceavo (1/14).
- ésimo/ésima, used only for ordinal tens: diez (10°), visésimo (20°), etc.
In addition, ordinal adjectives can sometimes be abbreviated and for this purpose the cardinal numbers and the suffix corresponding to the ordinal number are used, followed by a period. In this case, the gender needs of the referent are also respected. For example: primero becomes 1ero., segundo becomes 2do. and décima becomes 10ma.
On the other hand, there are some exceptions to the use of ordinal adjectives, such as in the case of primero and tercer, which when placed next to a noun lose their last vowel: “Cogimos el primero tren del día” and not “el primero tren del día”.
How do you convert a cardinal number into an ordinal number?
This transformation is extremely simple: just add the corresponding ordinal sign (°) next to the cardinal number to convert it into an ordinal number. If you want to write its name, you just need to learn the name of the corresponding ordinal number.
Ordinal numbers from 1 to 100
Below we can see the ordinal numbers from 1 to 100, with their respective names:
| Cardinal number | Ordinal number | Ordinal name (masculine, feminine) |
|---|---|---|
| 1 | 1st | first |
| 2 | 2nd | second |
| 3 | 3rd | third |
| 4 | 4th | fourth |
| 5 | 5th | fifth |
| 6 | 6th | sixth |
| 7 | 7th | seventh |
| 8 | 8th | eighth |
| 9 | 9th | ninth |
| 10 | 10th | tenth |
| 11 | 11th | eleventh |
| 12 | 12th | twelfth |
| 13 | 13th | thirteenth |
| 14 | 14th | fourteenth |
| 15 | 15th | fifteenth |
| 16 | 16th | sixteenth |
| 17 | 17th | seventeenth |
| 18 | 18th | eighteenth |
| 19 | 19th | nineteenth |
| 20 | 20th | twentieth |
