The word "you," when used in a sentence, is always used as "you are" rather than "you is". This happens regardless of whether the speaker is speaking to one person or many. Is "you are", when applied to a single person, an example of the numerous exceptions in the English language? Is there ever a situation where it is appropriate to use "you is"?
All English verbs except the full modals have three finite forms (finite forms are those which have tense, number and person):
- one form for present tense, 3d person singular ... full modals lack this form
- one form for present tense, all other persons and numbers
- one form fall past tense, all persons and numbers
The verb be, and only that verb, has two additional forms
- one form for present tense, 1st person singular: am
- one form for past tense, 1st and 3rd person singular: was
Here is a comparison of conjugations for be, love, and the full modal may:
PRESENT I AM we are I love we love I may we may you are you are you love you love you may you may he/she/it IS they are he/she/it LOVES they love he/she/it may they may PAST I WAS we were I loved we loved I might we might you were you were you loved you loved you might you might he/she/it WAS they were he/she/it loved they loved e/she/it might they might
So you are is not an exception; the exceptions are I am and I was. You is is not possible.
English used to have a distinct second person singular pronoun, thou, but dropped it in the course of the 16th and 17th centuries. It had its own verb forms,too (endings in -st, except be had the form thou art); but happily those were dropped, too; so there's that much less you have to to learn.
If there is an answer beyond "that's just the way it is" then it's back in the history of the development of the language.
I'm not convinced it's correct to call it an exception though. Are there languages which work the way you suggest, where the "you" equivalent takes a different form of the verb for singular versus plural? French and German are similar to English; in both cases the formal "you" (vous or sie) can be both singular or plural but the verb form is always the same; vous êtes or sie sind.
I know Spanish and Italian conjugate verbs differently for singular and plural you, but they also have different pronouns; they don't use different forms of the verb with the same pronoun.