How are plurals formed for letters, numbers, or signs?

When forming plurals for letters, numbers, or signs, using an apostrophe followed by 's' is the correct method. This approach helps to clarify that you are referring to multiple instances of the letter, number, or sign itself, rather than a grammatical possessive. For example, writing "two A's" or "the number 7's" makes it clear that you are discussing more than one of those symbols.

This method avoids confusion, particularly when items can easily be misread if simply pluralized with an 's' or 'es'. The apostrophe serves as a visual cue that differentiates these plural forms from standard plural nouns, helping maintain clarity in writing.