Merriam-Webster says it is: one who is polyglot. This annoyed me, I don't know who writes dictionaries nowadays, but my 6th grade English teacher taught me you cannot use the word you are defining in the definition of a word. Because, lets face it, it isn't helpful if you don't already know the meaning.
Cambridge Dictionary would make my 6th grade teacher a bit happier with: someone who can speak or use several different languages. However, the Cambridge Dictionary definition of several is some; an amount that is not exact but is fewer than many. So clear as mud. Their definition of many? a large number (of), or a lot (of):
Oxford Learners Dictionary give us: knowing, using, or written in more than one language, although this apparently is an American English definition.
Collins Dictionaries tells us that A polyglot is a person who speaks or understands many languages. So how do they define many? You use many to indicate that you are talking about a large number of people or things.
OK, so it seems many is slightly less than a large number of languages. So what is a large number? The only reference I could find with a decent definition was Wikipedia:
Large numbers are numbers that are significantly larger than those typically used in everyday life (for instance in simple counting or in monetary transactions), appearing frequently in fields such as mathematics, cosmology, cryptography, and statistical mechanics. The term typically refers to large positive integers, or more generally, large positive real numbers, but it may also be used in other contexts. The study of nomenclature and properties of large numbers is sometimes called googology
Excellent! So I'll get the definition of a large number from googology the study of large numbers. So, what is a large number?
Googologist Sbiis Saibian has defined a large number as: a large number is any real number greater than 1, Small numbers would be those smaller than 1.
So.... many, or large numbers are anything greater than 1. So a polyglot is anyone who speaks, writes, uses, more than one language. Note that the proficiency of usage isn't a determining factor here.
BTW, this all came up because someone called me a polyglot and I was going to prove them wrong.