The word thirtieth is one that often makes people pause when writing or speaking, especially if they are unsure about how to spell or pronounce it correctly. It represents the ordinal form of the number thirty and is used in various everyday contexts-such as birthdays, anniversaries, and dates. Although it may seem tricky at first, learning how to spell thirtieth is quite straightforward once you understand how English forms ordinal numbers. Let’s take a closer look at the correct spelling, its pronunciation, meaning, and how to use it naturally in writing and speech.
Correct Spelling of Thirtieth
The correct way to spell the word is thirtieth. It has nine letters and is written as
T-H-I-R-T-I-E-T-H
When broken down, thirtieth comes from the base number thirty plus the suffix -eth. This suffix is used in English to form ordinal numbers, which show position or order rather than quantity. For example, thirty refers to the number 30, while thirtieth refers to the position number 30 in a sequence-like the 30th day of the month.
Why People Misspell Thirtieth
Many English learners and even native speakers occasionally make mistakes with this word because of its unusual letter arrangement. Common misspellings include thirtith, thirteeth, or thirthieth. The confusion usually happens because the word changes form slightly from thirty to thirtieth-the y in thirty changes to i before adding -eth.
This spelling pattern is consistent with other ordinal numbers that end in y. For example
- Twenty → Twentieth
- Thirty → Thirtieth
- Forty → Fortieth
- Fifty → Fiftieth
As you can see, the rule is to drop the y and replace it with i before adding eth. Understanding this pattern helps you spell not just thirtieth but many other similar ordinal numbers correctly.
Pronunciation of Thirtieth
Thirtieth is pronounced as/ˈθɜːr.ti.ɪθ/in phonetic form. When spoken naturally, it sounds like THUR-tee-ith. The stress is on the first syllable THUR, which has the same sound as in thirty. The -ieth ending is softer and blends smoothly, so it’s not pronounced as a separate word but as part of the flow.
Here’s a breakdown of the syllables
- First syllable thir – sounds like thur, with the same vowel sound as in bird.
- Second syllable ti – sounds like tee.
- Third syllable eth – pronounced softly as ith.
Altogether, it becomes THUR-tee-ith. Practicing it a few times slowly can help with the rhythm and clarity of the word. It’s also worth noting that in casual conversation, native speakers often pronounce it quickly, making the ending sound less distinct but still recognizable.
Meaning and Use of Thirtieth
The word thirtieth functions as an ordinal number, which means it describes order or position. It answers the question which one? rather than how many? You’ll most commonly see it used when talking about dates, events, anniversaries, or rankings.
Examples of Thirtieth in Sentences
- Today is the thirtieth of October.
- She celebrated her thirtieth birthday with her family and friends.
- This is the company’s thirtieth anniversary since its founding.
- He finished in thirtieth place in the marathon.
- Their house number is the thirtieth on the street.
In all of these examples, thirtieth describes position or order rather than counting an amount. It’s also used both as an adjective (e.g., thirtieth day) and as a noun (e.g., the thirtieth of June).
How Ordinal Numbers Like Thirtieth Are Formed
To fully understand how to spell thirtieth, it helps to know how ordinal numbers work in English. Ordinal numbers show rank or position, and they are usually formed by adding certain endings to cardinal numbers (one, two, three, etc.).
Here’s a quick overview of how they’re formed
- 1 → First
- 2 → Second
- 3 → Third
- 4 → Fourth
- 5 → Fifth
- 10 → Tenth
- 20 → Twentieth
- 30 → Thirtieth
For most numbers ending in y, such as twenty, thirty, or fifty, the y changes to i before adding -eth. This simple rule makes it easier to remember the spelling for all similar ordinal numbers, including thirtieth.
How to Write Dates Using Thirtieth
When writing or saying dates in English, thirtieth is used to indicate the 30th day of a month. It’s typically written as 30th in numeric form, but when spelled out, it becomes thirtieth. For example
- October 30th → the thirtieth of October
- June 30th → the thirtieth of June
In spoken English, it’s common to use the ordinal form rather than the number. You would say, My appointment is on the thirtieth, not My appointment is on thirty.
Common Mistakes with Thirtieth
Even though thirtieth follows a logical pattern, there are a few common errors that people make when spelling or using it. Here are some to watch out for
- Using thirtyeth instead of thirtiethThe letter y in thirty changes to i before adding eth.
- Forgetting the eth endingWriting just thirty doesn’t indicate order; it needs eth to become an ordinal number.
- Pronouncing it incorrectlyRemember, it’s THUR-tee-ith, not THIR-tee-eth.
Paying attention to these small details helps ensure your spelling and pronunciation sound natural and accurate in all contexts.
How to Remember the Correct Spelling
One easy way to remember how to spell thirtieth is to think of the pattern -y to -ieth. Whenever you see a number ending in y, just replace it with ieth to create the ordinal form. Here’s a quick memory trick
- y says goodbye → ieth says hello
So thirty becomes thirtieth, forty becomes fortieth, and so on. This small spelling rule works for all similar words and makes learning ordinals much simpler.
Other Forms and Related Words
While thirtieth is the main form, it can appear in different grammatical contexts depending on how it’s used in a sentence. Here are some examples
- As a nounHe was the thirtieth to arrive at the party.
- As an adjectiveThey celebrated their thirtieth wedding anniversary.
It’s important to note that the spelling stays the same in all contexts. Only the way you use it in a sentence changes.
To sum up, the correct spelling of the word is thirtieth-T-H-I-R-T-I-E-T-H. It represents the ordinal number form of thirty and is pronounced THUR-tee-ith. The key rule to remember is that when forming ordinal numbers ending in y, you replace the y with i before adding eth. This simple pattern applies to words like twentieth, fortieth, and fiftieth as well. By understanding the spelling, pronunciation, and usage of thirtieth, you can write and speak English with greater accuracy and confidence. Whether you’re writing the thirtieth day of the month or celebrating your thirtieth birthday, this small yet essential word adds clarity and precision to your communication.