O or O.

1. Ohio (US state)
2. Old
3. Ordinary
4. Over(s) (cricket)

O grade or Ordinary grade noun

In Scotland, (a pass in) a former examination generally taken at the end of the 4th year of secondary education (also adjective, often with hyphen)

O level or Ordinary level noun

Esp in England and Wales, (a pass in) a former examination generally taken at the end of the 5th year of secondary education (also adjective, often with hyphen)

O

1. (as a medieval Roman numeral) 11
2. /ō/ oxygen (chem)

Ō

(medieval Roman numeral) 11000

O¹ or o /ō/

1. The fifteenth letter in the modern English alphabet, fourteenth in the Roman, derived from Greek omicron (Ο, ο), with various sounds, as in note, not, for, work, son, do
2. One of the four blood types in the ABO blood group system
3. In a series of numbers, nought or nothing
4. (usu in pl) a spangle (obsolete)
5. Anything shaped like the letter O

O² or oh /ō/

Used in addressing or apostrophizing, marking the occurrence of a thought, reception of information, or expressing wonder, admiration, disapprobation, surprise, protest, pain, or other emotion. The form O is chiefly used in verse (O for, O that)

Fifteen O's

Fifteen meditations on Christ's Passion, each beginning with O, composed by St Bridget

O's of Advent

Seven anthems each beginning with O, sung on the days before Christmas Eve

-o /-ō/ (slang or informal)

Used to form diminutives and abbreviations, eg wino, aggro

o’ or o /ō, ə/ a shortened form of of and on

O- /ō-/ (chem)

Signifying ortho-

O’ /ō/

In Irish patronymics, descendant of

• grandfather
• grandfather clause
• grandfather clock
• grandfathered
• grandfathering
• grandfatherly
• grandfathers
• grandfather's clock
• Grand Guignol
• grandiloquence
• grandiloquent
• grandiloquently
• grandiloquous
• Grand Inquisitor
• grandiose
• grandiosely
• grandiosities
• grandiosity
• Grandisonian
• grand juror
• grand jurors
• grand jury
• grand jésus
• grandkid
• grandkids