Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun o

3 senses of o

Sense 1
oxygen, O, atomic number 8 -- (a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust)
       => chemical element, element -- (any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter)
       => gas -- (a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely)

Sense 2
O, o -- (the 15th letter of the Roman alphabet)
       => letter, letter of the alphabet, alphabetic character -- (the conventional characters of the alphabet used to represent speech; "his grandmother taught him his letters")

Sense 3
O, type O, group O -- (the blood group whose red cells carry neither the A nor B antigens; "people with type O blood are universal donors")
       => blood group, blood type -- (human blood cells (usually just the red blood cells) that have the same antigens)