I've searched for whether "either" can be used in a context on which the possible options are made of more than two, and found the answer here over English Language Usage. It says that it is informal to use "either" on more than two options, but is used widely especially in oral communication.
However, he didn't mention that what is the best alternative to "either" in three or more options in formal context, and hence I posted this question here.
So, on the situation where there are multiple options possible, how should I express my sentence? For example, I want to know the alternative to this sentence:
I classify all pitches as either fastballs, breaking balls, or off-speed pitches.