ADJ

bottom, top
The top button of his shirt was undone
coat, shirt, etc.

VERB + BUTTON

do up, fasten
undo, unfasten
fumble with
lose
My coat has lost a button
rip off
sew on

BUTTON + VERB

be missing, come off, pop (off)
There was a button missing from his shirt

ADJ

on, start/starter
off, stop
control
fast forward, pause, play, rewind
alarm, panic
She hit the alarm button as fast as she could
mouse
self-destruct (often figurative)

VERB + BUTTON

click (on) (computing) , depress, hit, hold down, press, push
Click the left mouse button twice
keep your finger on
release, take your finger off

PHRASES

at the touch of a button
The remote control allows you to change channel at the touch of a button