Sentence examples for a size from inspiring English sources

"a size" is a correct and usable phrase in written English.
It is typically used to refer to the measurement or dimensions of something. For example: - The shirt comes in a size small, medium, or large. - The package was a size too big for the mailbox. - She requested a size five shoe, but they only had sizes four and six. - The hat was the perfect fit - a size that she had never found before.