Incorrect spelling, explanation: many users of English make a common mistake of spelling the word ninth as nineth. It is true that when we create ordinal numbers in English, we usually add the -th ending to a number so e.g. we have fourth, sixth or seventh. However, in the case of nine, when we add the -th ending, we need to remove the -e letter. Therefore, the only correct form is ninth.

Correct spelling, explanation: the word ninth comes from Old Germanic languages and it entered English in the times of Middle English, in which it appeared as nynte and nynthe. These forms are quite similar to the modern version, which is ninth and as a number written as 9th.

Definition of ninth:
1. ordinal number of nine, 9th as a word,
It is your ninth pair of shoes and they all look the same to me.
2. noun – one part from nine,
A ninth of twenty-seven is three.

Expressions with ninth:
Ordinal numbers are usually preceded by a definite article the. Some expressions with ninth include: be ninth, come in ninth.
The school year ends on the ninth of June this year.
He was ninth in the game, which did not satisfy him at all.
The team came in ninth in the world championship of football, which is a great result.