Números Ordinais De 1 A 100 Em Inglês

Aprender números ordinais em inglês é mais simples do que a maioria imagina, mas tem um detalhe que quase todo mundo erra na primeira vez.

Você provavelmente já sabe os cardinais — one, two, three, four — mas os ordinais seguem padrões que exigem atenção a regras específicas de formação. A maior parte funciona de forma previsível: adiciona-se o sufixo -th ao número cardinal. However, há exceções importantes que precisam ser memorizadas, e é nessas exceções que as pessoas cometem os erros mais frequentes.

Como formar os números ordinais de 1 a 100 em inglês

O básico é direto. Para a maioria dos números, basta adicionar -th ao final da forma cardinal. First, second e third são as únicas formas totalmente irregulares que você precisa decorar. A partir daí, a lógica se aplica consistentemente. Four vira fourth. Five vira fifth — observe a mudança de v para f. Eight vira eighth. Nine vira ninth, com apenas um n final. Sete vira seventh, mantendo os dois ns do original. Para os números compostos até cem, a regra é simples: apenas o último elemento recebe o sufixo ordinal. Twenty-one vira twenty-first. Thirty-five vira thirty-fifth. Cinquenta e oito vira fifty-eighth. O resto do número permanece inalterado.

Aqui está uma lista prática dos primeiros vinte, que são os mais usados no dia a dia: 1st — first
2nd — second
3rd — third
4th — fourth
5th — fifth
6th — sixth
7th — seventh
8th — eighth
9th — ninth
10th — tenth
11th — eleventh
12th — twelfth
13th — thirteenth
14th — fourteenth
15th — fifteenth
16th — sixteenth
17th — seventeenth
18th — eighteenth
19th — nineteenth
20th — twentieth

Os dezenas redondas seguem o mesmo padrão: twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety. Apenas adicione -eth. Note que forty perde o u em relação a fourty, que não existe — esse é um erro comum de soletração. Ao chegar a cem, temos hundredth. Entre vinte e cem, a estrutura é composta pelo número da dezena mais o sufixo -y e o ordinal do unidade. Twenty-second, thirty-third, forty-fourth. Nothing complicated about it.

I worked with international teams for years, and I once had to review a contract where the date was written as "August 32nd." That date doesn't exist, obviously, but the writer had confused the ordinal with the cardinal during a deadline rush. It sounds trivial, but getting these wrong in formal documents can create real ambiguity, especially in legal or technical contexts. One thing most learners miss is that ordinais são escritos com letras minúsculas quando aparecem no meio de uma frase. Only capitalize them when they appear at the beginning or in titles. The same applies to the abbreviation: you write 1st, 2nd, 3rd, and then 4th onward. The superscript notation is standard in most publishing, but in plain text without formatting options, writing 1st or 1/th both work. Most style guides prefer the superscript version.

Another nuance that trips people up involves the difference between ordinal numbers and fraction expressions. One third, two thirds — here "third" is a fraction, not an ordinal in the positional sense. They look the same but function differently in syntax. When you're talking about ranking or position, use the ordinal. When you're dividing something into parts, you're dealing with fractions, even though the word form is identical. The main bottleneck with learning ordinais is that spelling irregularities don't follow a single rule. Fifth, eighth, ninth, twelfth — each one has its own quirk. There's no shortcut around memorizing these. Flashcards and spaced repetition work well here. I found that writing them out by hand, ten or twenty at a time, cemented the spellings faster than any listening exercise I tried.

There's also a practical limit to how useful memorizing all one hundred ordinais is. In real usage, you'll rarely need anything beyond the 31st. Birthdays, deadlines, floor numbers, chapters — the vast majority of everyday contexts stay well within that range. Going past 100th is straightforward but rarely necessary unless you're working with dates far into the future or large-scale ordering tasks. If you want a quick reference sheet, most language learning sites offer printable versions. Duolingo, British Council, and Cambridge English all have free downloads. The British Council's list is the most accurate in terms of British pronunciation notes, which matters if you plan to use these in speaking exercises.

The biggest mistake I see is overthinking the whole process. People spend weeks trying to find patterns where none exist, then get frustrated when fifth doesn't follow the same rule as first or second. Just accept that the first three are exceptions, learn the tens pattern, and practice the spellings that don't follow the norm. That's all there is to it.