What is the part of speech for words suffixed with "ity"?

This may be a dumb question, but I am bad at grammar (software engineer).

Example: practical becomes practicality, equal becomes equality

The dictionary calls them nouns, but nouns are defined as

A word (other than a pronoun) used to identify any of a class of people, places, or things (common noun), or to name a particular one of these (proper noun).

What is confusing is that, by the above definition, the word practicality should be able to "identify any of a class of people, places, or things". So, what class of people, places, or things does "practicality" identify? What if people within that class aren't always practical?

What part of speech do these words fall into?

BONUS: is there such a version of the word empirical?

Answer

More specifically than being just nouns, nouns that are derived from adjectives by various different suffixes (-ness, -(i)ty, -(t/s)ion, -hood, -(e)ry, etc.) are known as abstract nouns, in that they refer to an entity that is not concrete or, as you yourself said in your comment, are not “a person, place, or thing”.

There are also abstract nouns that are not derived. Many of them, in fact. It is a fairly generic word class. When creating nouns by nominalising a verb gerund—i.e., taking the gerund running and using it as a noun, as in the phrase in the running—they usually become abstract nouns. There are exceptions (a winning is a concrete noun, as in the plural, one’s winnings), or cases where the resulting noun can be either depending on meaning (like a cutting from a newspaper, which is a concrete noun, as opposed to the cutting of a birthday cake); but most are abstract.

As regards your bonus question, the only abstract noun derived from the adjective empirical is empiricalness. Empiricality, while regularly formed, quite easily understood, and occasionally used (about 50,000 hits on Google), has not been picked up by any dictionaries and would probably be considered non-standard by most.