Io.

WordReference Random House Learner's Dictionary of American English © 2025

Io.,  an abbreviation of:

1. Place Names Iowa.

I/O,  an abbreviation of:

WordReference Random House Unabridged Dictionary of American English © 2025

i•o  (ē′ō), n., pl. i•os. 

1. Birds a small hawk, Buteo solitarius, having two plumage phases and occurring only on the island of Hawaii, where it is a rare species and the only living indigenous bird of prey. Also called Hawaiian hawk. 

• Hawaiian ‘io

I•o  (ī′ō, ē′ō), n. 

1. Mythology [Class. Myth.] a woman who, being loved by Zeus, was transformed into a white heifer and was, at the wish of Hera, first guarded by Argus and later pursued through the world by a gadfly until she reached Egypt, where she resumed her true shape: identified by the Egyptians with Isis.
2. Astronomy a large volcanically active moon of the planet Jupiter.

I•o  (ī′ō, ē′ō), n., pl. I•os. 

1. Chemistry, Insects See Io moth. 

Io, [Symbol, Chem.]

1. ionium.

Io., 

1. Place Names Iowa.

I/O, 

1. Naval Terms inboard-outboard.
2. Computing input/output.

I.O., 

1. Grammar indirect object.

Also, IO, i.o.