either, ether

Either or either ( pronounced "ee ther" or "eye ther", with a "th" as in "this" ), means a choice between two alternatives--
We can go to either show; the late screening starts at 9 p.m.
Do you want pizza or burgers? Either one is fine with me.

Ether or ether ( ee ther, with a "th" as in "thing" ) means the chemical that was once used as anesthesia, and for some manufacturing processes--
The Mad Hatter was crazy from breathing in the ether he used to treat the hats he made.
Before surgery, in the 19th century, they knocked people out by making them breathe ether.
Ether is also an old-fashioned term for air--
He dreamed of flying in the blue ether.

Now that you know that, you can say--
"Doctors once used either chloroform or ether to put people to sleep before an operation."