One-third is indeed correct as a fraction. It represents one out of three equal parts. When used as an adjective or adverb, it should be hyphenated, for example, “They got a one-third share” or “The money is three-quarters gone.” This is a common rule in English grammar for hyphenating fractions when they are used to describe or modify a noun.
Opinions, however, differ on whether fractions should be hyphenated when used as nouns. For instance, in the sentence “They got one-third of the money,” some style guides suggest hyphenating it as “one-third,” while others recommend leaving it as two separate words.
In my personal experience, I have seen both hyphenated and non-hyphenated forms used in different contexts. For formal or technical writing, such as in academic papers or official documents, it is generally recommended to hyphenate fractions when used as nouns. This helps to clarify that the fraction is being used as a single unit or entity.
On the other hand, in more casual or informal writing, such as in everyday conversations or informal emails, the hyphenation may be less strictly followed. In such cases, it may be acceptable to write “one third” as two separate words without the hyphen.
Ultimately, the decision of whether to hyphenate fractions when used as nouns may depend on the style guide being followed or the preference of the writer or editor. It is important to be consistent within a given context or document.
To summarize, one-third is correct as a fraction. Whether it should be hyphenated when used as a noun can vary depending on the style guide or the level of formality in the writing.