Key that a Mac lacks

ALT

This modifier is often paired with Ctrl or Shift on Windows keyboards but serves a different purpose on Apple devices, where its role is split between two other keys.

This clue plays on the fact that Mac keyboards don’t have a dedicated "Alt" key—instead, they use the "Option" key for similar functions. The word "lacks" hints that you’re looking for a key present on most PCs but missing (or renamed) on Macs. It’s a straightforward reference to keyboard differences, with "ALT" being the answer since it’s the key Macs technically don’t have.