'Thee' was an informal 'you' in English as it was spoken in the times of Shakespeare It is the object form. 'Thou' was the subject form. 'Thy' was the possessive. "Thou hast sold thy house" = You have sold your house. It was used with friends and family members. Now 'you' is used in both cases. I don't know the equivalent in Arabic, or if there is one.

Thou art more lovely and more temperate. thou=you art = are temperate = cool, not overcome by passion