Question

In musical notation, silence is indicated by

Answer 1

In musical notation, silences are indicated by a rest. A rest is a symbol that indicates the duration of the silence or pause. There are different rest symbols that correspond with specific note values for length that indicate how long the silence has to last.

Answer 2

It is indicated by a rest.
Rests include:
Quarter rests, half rests, and whole rests.

Bonus: if you happen to play in a band ensemble, there is such thing when you rest for more than a single measure or two.