Tips for Writing Your "Archaic Language" Poem

WHEN TO USE “THOU” AND WHEN TO USE “THEE,” and also WHEN TO USE “THY”:

The word "thou" is a second person singular pronoun in English. It is now largely archaic, having been replaced in almost all contexts by you.

"Thou" is the nominative form: the subject of the sentence.
Example: Thou hast such lovely eyes.
(modern translation: You have such lovely eyes.)

Verbs following thou often have the endings -st or -est; for example: "thou goest."

"Thee" is the oblique/objective form. Use it when the target is the object on which the verb acts.
Example: I give my love to thee.
(Modern translation: I give my love to you.)

"Thy" is the archaic equivalent of “your.” It is the possessive.
Use "thy" to replace “your,”
but use “thine” if the noun following starts with a vowel.

Example a) Thy face is lovely.
(Modern translation: Your face is lovely.)

Example b) Thine eyes art lovely.
(Modern translation: Your eyes are lovely.)

“Thine” is also used to replace “yours”
Example: My heart is thine.
(Modern translation: My heart is yours.)

Originally, “thou” was simply the singular counterpart to the plural pronoun “ye.”
“Thou” was later used to express intimacy, familiarity or even disrespect,
while “you” was used for formal circumstances.