oh

from The American Heritage® Dictionary of the English Language, 5th Edition.

• interjection Used to express strong emotion, such as surprise, fear, anger, or pain.
• interjection Used in direct address.
• interjection Used to indicate understanding or acknowledgment of a statement.
• noun Zero.

from The Century Dictionary.

• An abbreviation of Old High German.
• See O.

from the GNU version of the Collaborative International Dictionary of English.

• interjection An exclamation expressing various emotions, according to the tone and manner, especially surprise, pain, sorrow, anxiety, or a wish. See the Note under o.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• interjection Expression of surprise.
• interjection Expression of wonder, amazement, or awe.
• interjection Expression of understanding, recognition, or realization.
• interjection A word to precede an offhand or annoyed remark.
• interjection A word to precede an added or comment or afterthought.
• interjection An invocation or address (similar to the vocative in languages with noun declension).
• interjection Exclamation for drama or emphasis (often poetic).
• interjection Expression of pain. See ouch.
• interjection Space filler or extra syllable, especially in (popular) music.
• interjection Used with a term of endearment.
• interjection interrogative Expression of mild scepticism
• noun the letter O, o (more commonly spelled o)
• noun the digit 0 (especially in representations of speech)
• noun An utterance of oh; a spoken expression of surprise, acknowledgement, etc.
• verb intransitive To utter the interjection oh; to express surprise, etc.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a midwestern state in north central United States in the Great Lakes region