Nineth or Ninth: Which Spelling Is Correct?

Ninth is the correct spelling. Nineth, spelled the way the pattern seems to demand — nine plus -th — is a misspelling, and a particularly stubborn one, because the logic behind it is almost right. Most ordinal numbers are formed by adding -th to the cardinal number: four → fourth, six → sixth, ten → tenth. By that pattern, nine should become nineth. It does not. The e drops out first, giving ninth, and that one missing letter is the whole difference between the correct spelling and the error.

This guide explains what ninth means in its three uses — as an ordinal, as a fraction, and in music — why the e disappears, how the word is pronounced, and how the ordinal numbers work as a system, so that ninth stops looking like an exception.

What Does “Ninth” Mean?

Ninth is the ordinal form of the number nine — the word for the thing in position number nine in a series. Collins defines it as an ordinal number: the ninth item in a series is the one you count as number nine. Cambridge gives the same first sense (“9th written as a word”) and adds two more: one of nine equal parts of something, and, in music, the distance between two notes.

1. The ordinal: position nine

This is the use most people mean most of the time. The ninth month is September. The ninth floor is eight floors above the ground floor. The ninth person in the queue is the one with eight people in front of them. Ordinal numbers answer the question “which one in the order?” rather than “how many?”, and ninth answers it for the number nine.

• “September is the ninth month of the year.”
• “She finished ninth in the race.”
• “He was the ninth person to walk on the moon.” (Edgar Mitchell, Apollo 14 — the example Cambridge itself uses.)
• “We live on the ninth floor.”

2. The fraction: one of nine equal parts

Ninth is also a noun meaning one of nine equal parts: “a ninth of the cake”, “two ninths of the voters”. The plural is ninths, and the rule for reading fractions applies: use the cardinal number for the numerator and the ordinal for the denominator, making the ordinal plural when the numerator is larger than one — “one ninth”, “two ninths”, “five ninths”. The spelling is the same in both uses, which is convenient: learn it once and it covers both.

3. The musical interval

In music, a ninth is the interval between two notes nine scale degrees apart — an octave plus a second. It appears in chord names (“a ninth chord”, “add9”). This use is specialist, but it follows the same spelling.

Why “Nine” Becomes “Ninth”, Not “Nineth”

The rule for most ordinal numbers is simple: add -th to the cardinal number. Four → fourth, six → sixth, seven → seventh, ten → tenth, eleven → eleventh. But a small group of numbers change their spelling before the suffix is added, and nine is one of them. The final e drops out, and -th is added directly to the n: nine → ninth.

The group is small enough to learn as a set:

Cardinal	Ordinal	What changes
one	first	Completely irregular
two	second	Completely irregular
three	third	Completely irregular
five	fifth	ve becomes f
eight	eighth	t becomes th (the h is added)
nine	ninth	Final e drops
twelve	twelfth	ve becomes f
twenty	twentieth	y becomes ie

Why does the e drop? The spelling reflects the word’s history rather than a tidy rule. The Old English ordinal was nigoþa, which came down through Middle English as nynthe and nynte before settling as ninth. The useful parallel is five → fifth and twelve → twelfth: in each case the end of the cardinal word changes shape to make room for the -th.

How to Pronounce “Ninth”

Ninth is pronounced /naɪnθ/ in both British and American English — “nynth”, one syllable, rhyming with thine plus a th at the end. The i is the long vowel of nine itself, and the final sound is the voiceless th (/θ/), the same sound as in think and teeth — not the voiced th (/ð/) of this and teethe. The n and the th sit next to each other, which makes the end of the word slightly awkward to say; take it slowly and the two sounds separate cleanly.

The misspelling nineth would, if pronounced by the rules, add a syllable — “NY-neth” — which is not how anyone says the word. Pronunciation is therefore a useful check: say the word as one syllable, hear the n run straight into the th, and the spelling without the e follows.

Ordinal Numbers: The System “Ninth” Belongs To

Ninth is easier to remember as part of the ordinal system than as an isolated fact. The system has four suffixes and a handful of exceptions, and once you know them, every ordinal from first to hundredth falls into place.

The suffix depends on the last digit: 1 takes -st (first, 21st), 2 takes -nd (second, 22nd), 3 takes -rd (third, 23rd), and everything else takes -th (fourth, sixth, ninth, tenth). The exception is the teens: 11, 12, and 13 always take -th (11th, 12th, 13th), never -st, -nd, or -rd.

In words, the ordinals from one to twenty run first through twentieth, with ninth in its place between eighth and tenth. From twenty-one onwards, only the last part changes: twenty-first, twenty-second … twenty-ninth, thirtieth. Compound ordinals are hyphenated when written out: twenty-ninth, ninety-ninth — the same dropped e in every compound ending in nine.

“Ninth” in Real Sentences

• “September is the ninth month of the year.”
• “She came ninth out of forty runners.”
• “Today is the ninth of June.”
• “He lives on the ninth floor of the building.”
• “Two ninths of the budget went on transport.”
• “The ninth chapter is the longest in the book.”

Correct vs Incorrect

Incorrect	Correct	Why
September is the nineth month.	September is the ninth month.	Nine drops its e before -th.
She finished nineth in the race.	She finished ninth in the race.	The ordinal of nine is ninth, 9th.
The twenty-nineth of June	The twenty-ninth of June	Compounds keep the same dropped e.
Two nineths of the cake	Two ninths of the cake	The fraction plural is ninths, not nineths.
On the 9’th floor	On the 9th floor	No apostrophe between the number and its suffix.
The nineth Symphony	The Ninth Symphony	Beethoven’s Ninth — capitalised as part of the title, spelled ninth.

Common Mistakes to Avoid

1. Adding “-th” to “nine” without dropping the “e”

This is the central error, and it follows from a real pattern applied one step too far. Most ordinals do just add -th, and nineth looks like it should work. It does not, because ninth is one of the small group of ordinals that change spelling first. Learn ninth alongside fifth and twelfth, the other two members of the group, and the three will reinforce each other.

2. Writing “nineth” in compounds

The error travels: writers who spell the simple ordinal as nineth also write twenty-nineth, thirty-nineth, and ninety-nineth. The fix is the same in every case — the last part of a compound ordinal is the simple ordinal, spelled the same way: twenty-ninth, thirty-ninth, ninety-ninth.

3. Confusing ordinals with cardinals in dates

“June nine” and “the ninth of June” are both heard, but in writing, dates take the ordinal: “the 9th of June” (British) or “June 9th” (American). Writing “June nine” in a formal document reads as an error, and writing “June nineth” compounds it. Use the ordinal, spelled ninth.

4. Adding an apostrophe to “9th”

9’th appears surprisingly often, probably by analogy with possessives and contractions. There is no omitted letter in 9th — the suffix is added directly to the number — so there is nothing for an apostrophe to mark. Write 9th, with no punctuation between the digit and the letters.

How to Remember the Spelling

Three memory aids, in order of usefulness. First, pair it with “fifth”: five → fifth and nine → ninth both lose a letter before -th, and learning the pair together makes each one harder to get wrong. Second, count it out: say the ordinals from first to tenth aloud and listen for the rhythm — ninth sits between eighth and tenth, and the sequence sounds wrong with nineth in it. Third, think of the number 9: the e of nine is the extra piece, and the ordinal drops it.

The pattern of letters dropping before a suffix is a wider feature of English spelling. If you want to see the same idea at work in a different word, Clarifyra’s guide to comprable or comparable shows how a root word’s letters behave when a suffix is added.

FAQs

Is “nineth” ever correct?

No. Ninth is the only standard spelling of the ordinal of nine. Dictionaries such as Merriam-Webster and the Oxford English Dictionary list only ninth, and nineth is recorded as a misspelling, not as a variant. It is the same in British and American English — there is no regional difference.

Why is it “ninth” and not “nineth”?

Because nine drops its final e before the ordinal suffix -th. It belongs to a small group of ordinals that change spelling before the suffix, alongside five → fifth and twelve → twelfth.

How do you pronounce “ninth”?

/naɪnθ/ — one syllable, “nynth”, with the voiceless th of think at the end. The pronunciation is the same in British and American English. The misspelling nineth would suggest two syllables, which is not how the word is said.

What is the abbreviation for “ninth”?

9th — the number 9 with the last two letters of the word attached, and no apostrophe. The same pattern gives 1st, 2nd, 3rd, and 4th onwards, with 11th, 12th, and 13th as the exceptions to the 1/2/3 rule.

Is it “twenty-ninth” or “twenty-nineth”?

Twenty-ninth. Compound ordinals use the simple ordinal as their last part, spelled the same way, and hyphenated: twenty-ninth, thirty-ninth, ninety-ninth.

The Takeaway

Ninth is correct; nineth is not. The pattern that suggests nineth is real — most ordinals do just add -th — but nine is one of the few numbers that changes first, dropping its e the way five becomes fifth. Learn it with fifth and twelfth and the spelling will stop looking like an exception. If you need to confirm the entries, see ninth in Collins and ninth in Merriam-Webster.