Marks, Quotes and Primes
There are many criteria to consider when selecting a typeface for your design projects. One of them is whether a type family contains proper quote marks and prime marks in their complement of glyphs.
Unfortunately, a lot of type heritage on computers is from typewriters, which could only type a finite number of glyphs. It was a mechanical limitation of all typewriters.
Double Quote Marks
Avoid using prime marks, or dumb quote marks to quote text. Use proper double curly quotes instead. Quote marks should not be used for emphasis.
What’s shown above are proper double curly quote marks.
Single Quote Marks
Single quote marks are used for a quote inside another quote. They should also be curly or curved.
What’s shown above are proper single curly quote marks.
The apostrophe is used for contractions, like can’t. It’s a also used to indicate the possessive case of nouns, like the boy’s bicycle. It can also mark plurals, as in watch your p’s and q’s and the 1950’s.
The apostrophe should also be curly. It’s the same glyph as the single closing quote mark.
Interestingly, in the typeface Tisa by FontFont, the typographer designed a distinct apostrophe glyph.
Note how the apostrophe sits lower, near the x-height. The single closing quote is at the cap height. This is very unusual, but a welcome addition.
Prime marks are used in a mathematical context, as shown below. They’re sometimes called dumb quotes or tick marks. They’re properly called primes.
Avoid using these marks to quote text, unless you have no choice. Note that many monospace typefaces have no proper curly quote marks because of their provenance on the typewriter.
You can read more on this topic at Butterick’s Practical Typography site.