What Is The Difference Between 21th And 21st? – All The Differences

Steven Hayes
By Steven Hayes 15 Min Read
15 Min Read


Here, we delve into the perplexing distinction between the numerical suffixes “21st” and “21th”. It is crucial to understand that ordinal numerals require the correct suffix, and using the wrong one can lead to grammatical errors. The 21st century denotes an era from 2001 to 2100, whereas 21th has no relevance in terms of date. Let’s explore the nuances of these two suffixes further.

It’s worth noting that adding “th” as a suffix is incorrect when referring to ordinal numbers ending with 1 or 2. We use “st” for 1st, “nd” for 2nd, and “rd” for 3rd. However, after 3rd, we add “-th,” such as 4th, 5th, and so on. The same rule applies to decades, such as the ’90s (1990s). Therefore it stands true that we use only ‘21st‘ for denoting years from year ‘2001‘ onwards.

Don’t let incorrect usage of these suffixes give your writing a sloppy appearance or diminish reading comprehension by making it harder for readers to interpret your meaning. Correctly using them can lead to better communication and understanding in both written and spoken contexts. Keep an eye out for them when proofreading your work.

Understanding these fundamental distinctions between ordinal numerical suffixes is vital knowledge that every communicator should have in their arsenal. Don’t miss out on mastering this crucial aspect of language; make sure you’re getting it right every time you write!

Ordinal numbers sound fancy, but they’re just numbers with a bit of attitude and a whole lot of ranking power.

Definition of Ordinal Numbers

Ordinal numbers are numerical values that indicate sequential order or position in a series. These types of numbers differ from cardinal numbers, which denote quantity. When we talk about the ordinal number 21st or 21th, we are referring to the order or position of the number 21 in a series. The difference between the two lies in their spelling and pronunciation.

In the English language, ordinals from 1 to 20 end with “th”, “st”, “nd” and “rd”. However, outside this range all ordinal numbers end with “th”. For example, we use 1st for first ordinal, 2nd for second ordinal, 3rd for third ordinal and so on up to the ordinal twenty (20th). But when it comes to numbers beyond twenty, like the number twenty-one (21), we stick with adding suffix “-th” at the end of most numeric forms (like twenty-first) except for those who have a specific endings like thirty-first or seventh.

It is essential to note that these spelling rules apply only to written form while pronouncing both will remain equivalent. Whether you pronounce it as “twenty first” or “two one st”, you are still referring to the same thing; hence there’s no difference in meaning.

Although there isn’t much history associated with this heading since its representation has been consistent over time and languages all throughout history. Regardless of what language you speak or write, understanding ordinal numbers is critical if you want to express yourself accurately and precisely while speaking about numbered positions within a series.

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Learning these suffixes may be the 21st thing you do today, but it’s worth it for all the 22nd and 23rd things you’ll understand later on.

Understanding the Suffixes Used in Ordinal Numbers

To understand the suffixes used in ordinal numbers like 21st or 21th, and avoid confusion in your writing, go through this section: “Understanding the Suffixes Used in Ordinal Numbers”. This will cover the most common suffixes used, such as the -st and -th suffix.

-st suffix

The suffix denoted by ‘-st‘ is an essential part of ordinal numbers, indicating the position of something in a series. It is added to the end of a cardinal number to form an ordinal number, e.g. 1st, 2nd, 3rd. Interestingly, only numbers from 1 to 9 use this suffix; for higher numbers, the ‘-th‘ suffix is used instead.

This simple yet powerful suffix can help differentiate between items and their order in a list or sequence. Its usage follows basic grammatical rules; for instance, when the base number ends with ‘y‘, it changes to ‘i‘ before adding ‘-st‘. Exceptions include irregular words like ‘first‘, which do not follow this rule.

While being commonly used in everyday language, it has implications in scientific contexts too. In bioinformatics fields where names are assigned to genes in sequential order, ‘-st‘ reflects their position on chromosomes. They become distinct from other genes with similar names and further ease their indexing and retrieval.

Interestingly, the origin of ordinal suffixes dates back to Old English times when they were written as separate words such as “firða” for fourth or “fifta” for fifth. The current format emerged later during Middle English time and evolved over centuries into its standardized form we use today.

They say ignorance is bliss, but with the ‘-th‘ suffix, it’s just blissfully ordinal.

-th suffix

Ordinal numbers are formed by adding a suffix to the base number. The most common suffix used for forming ordinal numbers is ‘-th’. It is added to the end of the base number, such as one becomes first or five becomes fifth.

The ‘-th’ suffix is used in English to create ordinal numbers that denote position or sequence, such as first, second, third and so on. These ordinal numbers are used in a variety of contexts, including dates, rankings and measurements.

It’s important to note that not all ordinal numbers use the ‘-th’ suffix. For example, some ordinal numbers use ‘-st’, like first or twenty-first; others use ‘-nd’, like second or thirty-second; and still others use ‘-rd’, like third or forty-third.

To create ordinal numbers correctly, it’s essential to understand which suffix should be used with each base number. Remembering these rules can help you avoid making errors when writing or speaking about positions or sequences. To strengthen your knowledge of creating ordinal numbers, make it a habit to practice writing them frequently with different base numbers.

Why settle for 21th when you can aim for 21st and be the best of the bunch?

Differences between 21st and 21th

To understand the differences between “21st” and “21th” in writing, the suffixes of ordinal numbers play a vital role. Are you confused about the correct usage of these suffixes? Don’t worry! This section on the differences between 21st and 21th with sub-sections, “Meaning of the suffixes in 21st and 21th,” “Proper usage of the suffixes in writing,” and “Common Mistakes to Avoid When Using 21st and 21th,” will help clarify all your doubts.

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Meaning of the suffixes in 21st and 21th

The meaning of the suffixes in 21st and 21th lies in the ordinal numbers used to represent them. These numbers denote the position of a century or year in a sequence. The suffix ‘-st‘ is used for the first nine ordinal numbers, while ‘-th‘ is used for all other numbers.

Meaning of the Suffixes in 21st and 21th

Ordinal Number Suffix Used
1 st
2 nd
3 rd
4-9 th
10 and above th

Understanding this difference between ‘st‘ and ‘th‘ helps in accurate representation of centuries and years.

It’s important to note that using abbreviations such as ‘nd‘ or ‘rd‘ instead of the full suffix may result in ambiguity or confusion, especially when written without context.

To avoid such confusion, using the full suffixes is recommended. Additionally, including context whenever possible can further clarify references to specific ordinals.

Improper use of suffixes is the grammatical equivalent of wearing socks with sandals.

Proper usage of the suffixes in writing

The precise usage of suffixes in writing is crucial to convey the intended meaning. Improper usage can lead to confusion and errors in communication. Here’s a breakdown of how to appropriately use 21st and 21st in your writing.

Suffix Correct Usage Incorrect Usage
-st 21st, 22nd, 23rd, etc. 21th, 22th, 23th, etc.

It’s essential to note that ordinal numbers use -st for the first nine numbers only. From ten onward, you add -th as a suffix. Additionally, the suffix -nd is added for second and the suffix -rd for third.

One common mistake to avoid is using ‘21th‘ instead of ’21st’. This error can happen due to a lack of understanding about the rule outlined above.

Ensure you use proper suffixes correctly when writing ordinal numbers. Not doing so can lead to misinterpretation or misunderstanding. Remember, accuracy in language goes a long way in professional communication.

Make sure to double-check your work before submitting or sending it out. The last thing you want is to miss out on an opportunity due to an easily avoidable error like incorrect suffix usage.

Don’t be the person who confuses ‘21st century‘ with ‘21th century‘, unless you want to be known as the resident time traveler with bad grammar.

Common Mistakes to Avoid When Using 21st and 21th

The correct usage of ’21st’ and ’21th’ is crucial in professional settings. Avoiding common errors when differentiating them can help us present ourselves more confidently. Below are the four significant mistakes that one must avoid when using these terms:

  • Using “21th” instead of “21st”
  • Using ordinal adverbs like “secondly”
  • Sequencing events using “first”, “second” and so on.
  • Failing to recognize the significance of the correct terms for resume writing

It is essential to ensure consistency in the use of these numbers throughout a document or sentence where needed.

Interestingly, despite being common knowledge, many people still misuse these phrases even in professional documents. A closer look at history shows that these mistakes date back as far as the medieval times when scribes miswrote Roman numerals in manuscripts.

So, if 21st and 21th confuse you, just wait till you try to figure out 69th and 69st.

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Other Examples of Ordinal Numbers with -st and -th suffixes

Ordinal numbers are used to indicate position or order. In English, many ordinal numbers end with the suffixes -st and -th. There are many other examples of ordinal numbers with these suffixes that are commonly used.

Number Suffix
1 st
2 nd
3 rd
4-20, 30, 40, 50, etc. th

In addition to these common examples, there are also several unique ordinal numbers that end in -st and -th suffixes. These include “21st”, “31st”, “42nd”, and “53rd”.

One interesting fact about ordinal numbers is that the use of the -th suffix was not always standard practice. In Middle English, the -th suffix was only used for a select few words, while other words would use different endings such as -inde or -eode. It wasn’t until later on that the use of the -th suffix became widespread.

Understanding the various examples of ordinal numbers and their suffixes can be helpful in accurately conveying information about position and order in written or spoken communication.

I hope this article has brought you one step closer to knowing the difference between 21th and 21st, because let’s face it, it’s not something you want to get wrong on your next birthday card.


After delving into the intricacies of 21st and 21th, it can be surmised that the fundamental disparities between the two lie in their ordinal suffixes. While “st” denotes first, second or third, “th” is used for all other ordinal numbers. These subtle differences can significantly affect our writing accuracy.

It’s important to note that the use of each suffix depends on the specific number that follows. Ordinal numbers ending in a digit from one to three take “st,” while those ending in four to nine take “th.” This applies to any number that isn’t a multiple of ten.

In addition to this, when writing dates or years, we always use “st,” “nd,” and “rd” for the first three ordinal numbers respectively, followed by “th” for all others. Knowing these nuances will help writers avoid errors and bring precision to their work.

Pro Tip: It’s crucial to pay attention to small details like these as they can make a significant difference in one’s professional writing.

Frequently Asked Questions

What is the difference between 21th and 21st?

The correct ordinal form of the number 21 is 21st, not 21th.

Why is 21st the correct ordinal form?

The last two letters of the word the ordinal number is being applied to determine the suffix. "st" is the correct suffix for numbers ending in 1.

What is the significance of using the correct ordinal form?

Using the correct ordinal form is important in formal writing and speaking to prevent errors and show attention to detail.

Is this a common mistake people make?

Yes, it is a common mistake, especially among non-native English speakers and those who are not familiar with English language rules.

Can using the incorrect ordinal form change the meaning of a sentence?

In most cases, using the incorrect ordinal form does not change the meaning of the sentence but can cause confusion or make the writer/speaker appear less credible.

What are some other examples of ordinal numbers?

Other ordinal numbers include 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th, 13th, 14th, 15th, 16th, 17th, 18th, 19th, 20th, 22nd, 23rd, 24th, and so on.

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