Readers of Shakespeare and Early Modern versions of the Bible (e.g. Douay-Rheims/King James) are doubtless aware that English as it is spoken today is considerably ‘defective’ (in the grammatical sense) compared to the way it was spoken and written several centuries ago. The second-person pronoun, you, is the most obvious example, having lost all of its forms except for that of the plural object. This situation causes a perplexity when one tries to translate other languages into English: how to render differences in the second-person pronouns of other languages when English has only the one form?
In the interest of recovering those lost forms, whether for translation purposes or everyday use(!), I provide here a much simplified set of basic instructions for forming second- and third-person pronouns and their associated verb endings:
2nd Person Singular Subject: Thou (Thou art running.)
2nd Person Singular Object: Thee (I hit thee.)
2nd Person Plural Subject: Ye (Ye are applauding.)
2nd Person Plural Object: You (I dismiss you.)
2nd Person Singular: -t/st (Thou shalt not lie. Thou hast the cup.)
3rd Person Singular: -th (He/She/It hath value.)
2nd Person Singular: Thy (I see thy cat.)
2nd Person Singular before vowel sounds, or as a pronoun: Thine (I see thine eyes. The cup is thine)
(1st person my/mine is formed likewise: my cat, mine eyes, the cup is mine).
The English second person pronoun became defective in part due to social convention. The plural form (Ye/You) was also used as the formal mode of address when speaking to individuals. In time, two things happened: (1) people were increasingly keen to demonstrate that they treated everyone very respectfully, so the formal mode of address was used in ever-less-formal settings; and, (2) people began to expect to be addressed formally, so the formal mode of address was used in order to avoid giving offence. George Fox wrote that some Quakers–who generally adhered to grammatical convention–were accosted in the street when they failed to address individuals with the formal, plural pronoun. Despite that, some Quaker communities continue to use Thy/Thou; and, in regions such as Yorkshire and Durham, the second person Thou/Thy is also still in use.
There are some fine resources online for a more detailed account of Middle and Early Modern English grammar. But, as far as print resources go, I recommend Fisiak’s A Short Grammar of Middle English (1968), which provides the grammatical background for the forms above (pp. 86-87).