Quotation marks around single words can occasionally be used for emphasis, but only when quoting a word or term someone else used. Usually, this implies that the author doesn’t agree with the use of the term.
When quotation marks are put around a word in this way, they are called scare quotes.
The rules for using quotation marks around a single word for emphasis have changed since people began using word processors for their writing. If a word needs to be emphasized but is not being quoted, you should avoid putting the word in quotes and use italics instead. If you are writing by hand or using a typewriter, you can use quotation marks for emphasis to separate a certain word from the rest of the sentence—for example, when you are writing about words as words:
For further information on using quotation marks, check out our article Quotation Marks: Grammar Rules.