Option key

The Option Key (⌥), is the Mac equivalent of the on PCs (and so labeled on some Mac keyboards).

History
The "Option" key first appeared in January 1983 on keyboards that were included with Apple Lisa computer systems. It replaced the functionality of the "closed" or "solid" Apple logo () modifier keys of the preceding Apple III computer systems.

The "alt" notation first appeared in 1987 (appearing along with "Option") on the Apple Extended Keyboard for the Macintosh SE and II. The "⌥" symbol first appeared in 1990 on international versions of the Apple Extended Keyboard II.

International keyboards sold outside of the United States between 2006 and 2017 omitted the "Option" label, only identifying with key with "alt" and "⌥" markings. This was known to have caused confusion among some users. Starting in 2017, the keys were internationally standardized to be identified with "⌥" and "Option" markings.