The
Macintosh keystroke to
signal that you wish to type a
letter with an
umlaut or
dieresis over it. The
Macintosh can display a
dieresis over an
a,
e,
i,
o,
u, or
y; these
characters are used in various
languages, including
German.
See also: option key, option-e, option-n, option-i, option-`.