thou

Originally the singular second person pronoun in English; at that time "you" was always plural. Eventually "you" became formal and "thou" became informal, and to be polite people generally used the formal form. The Friends (Quakers) felt that no one deserved to be elevated above others, so they always used the informal form and preserved it.

Gorgonzola notes: "I would hope that when using 'thou', people also use the appropriate verb conjugation (thou art, thou wert, thou hast, etc)."

This is a common mistake actually, so common that it's not considered a mistake any more.
The fact is that "thou" is the second person singular, and "you" is the second person plural.

Here's an example:
"Art thou going to the theatre with me?" - That is only one person, it can't be mistaken for:
"Are you (lot) going to the theatre with me?" - In modern English, this could be either singular or plural, (hence the "lot" which I added to make it plural for this example.)

Yeah, thou arst a poncy bastard if thou actually speak like this, but at least take note.

No offence to god though..

You know what's funny? I just realised I made the mistake I noded about in my title. Har Har.

Cast of Thousands, chapter 8

Somehow she made it to German class without falling asleep.

"Open your books to page forty eight," Fraulein Schau ordered. "We'll be listening to the dialogue between Friedrich und Frau Braun, and then splitting into pairs to read it together. Is everyone ready?" She put a tape into her boom box without waiting for an answer.

They listened to the tape, Jessica following the words with her finger and mouthing them to herself. As the dialogue came to an end, Fraulein Schau turned it off and smiled benignly at them all. "Has everyone found a partner?"

They scrambled to grab one another. Jessica felt a tap on her shoulder and turned hurriedly to see Harley, who had been in her elementary school class for the last four years. They did not know each other well,.but any familiar face was welcome in the wilds of junior high school.

She dragged her desk around a half-turn to face Harley. The girl read her simplistic conversational gambit sarcastically, her dozens of skinny braids swinging.

"Nein. Mein Mann ist Deutscher," Jess replied obligingly, if stiltingly.

Harley smirked at Jess over the text, and added, "Ha ha! You have a man!"

Jessica laughed, and then covered her mouth in horror as Fraulein Schau paused by her desk.

"Is something funny, girls?" she said gently, but with a warning edge. "Let us hear it."

They read the text again, meekly, and all the way through this time.

"Sehr gute," the teacher said, moving on.

"Ohh, she makes me sweat," Harley groaned, putting her head down on her desk.

"She probably doesn't mean to, Jessica said amiably.

"Don't you believe it. That woman knows how to keep us in line. Ugh," her friend shuddered.

"Eyes to the front, class!" Fraulein announced, and everyone rushed to turn around.

"See what I mean?" Harley hissed daringly in Jess' ear.

"Why does Friedrich use the formal form of the verb? Hm? Anyone?" Fraulein Schau gazed around at each of them slowly. "Ryan?"

A stoutly freckled boy in a green football jersey jumped nervously. "Uh, because he was talking to his teacher, Fraulein Schau?"

"And what does that tell us?" Her gaze swept across them again. "That she is his elder and also that she is a figure of respect to him. In English we do not have this form of the verb, do we?" She seemed to be waiting for an answer. A few scattered voices mumbled, "No, Fraulein Schau."

"No. But that is not quite correct. Have any of you read Shakespeare, or Chaucer? The old authors?"

Jessica had chipped away at a little of both in her mornings at the library. She raised her hand halfway, and the teacher pounced. "Romeo would have called his teacher 'you' to indicate respect would he not? And what form would Romeo have used casually with his friends, Fraulein Pullman?"

"Uh... thou?" Jessica answered timidly.

"Thou, Fraulein Schau," the teacher corrected her, lengthening the "au" sounds till she seemed to toll the correction like a bell. "That is so. This separation of 'you' and 'thou' or 'thee' has fallen by the wayside, now, and with it the notion of au-to-ma-ti-cal-ly respecting one another. Think about this, class." The bell shrilled again, and she raised her voice above it easily. "We will discuss it further next week. Be off!"

Jessica found herself outside the classroom, books and bag in hand, without quite knowing how she had escaped so quickly. Harley was swept past her in the rush of students, shooting her a wry grin.

Chapter 9?

Thou (?), pron. [Sing.: nom. Thou; poss. Thy (?) or Thine (); obj. Thee (?). Pl.: nom. You (); poss. Your (?) or Yours (); obj. You.] [OE. thou, þu, AS. ðū, ðu; akin to OS. & OFries. thu, G., Dan. & Sw. du, Icel. þū, Goth. þu, Russ. tui, Ir. & Gael. tu, W. ti, L. tu, Gr. συ`, Dor. τυ, Skr. tvam. 185. Cf. Thee, Thine, Te Deum.]

The second personal pronoun, in the singular number, denoting the person addressed; thyself; the pronoun which is used in addressing persons in the solemn or poetical style.

Art thou he that should come? Matt. xi. 3.

⇒ "In Old English, generally, thou is the language of a lord to a servant, of an equal to an equal, and expresses also companionship, love, permission, defiance, scorn, threatening: whilst ye is the language of a servant to a lord, and of compliment, and further expresses honor, submission, or entreaty."

Skeat.

⇒ Thou is now sometimes used by the Friends, or Quakers, in familiar discourse, though most of them corruptly say thee instead of thou.

© Webster 1913.

Thou, v. t.

To address as thou, esp. to do so in order to treat with insolent familiarity or contempt.

If thou thouest him some thrice, it shall not be amiss. Shak.

© Webster 1913.

Thou, v. i.

To use the words thou and thee in discourse after the manner of the Friends.

© Webster 1913.

[Editor's note, 12/30/2010: Minor HTML entity repair.]