How to genrate sawtooth wave by using ujt?

A: add a capacitor and proper bias

The sinusoidal wave is harmonically pure, i.e. it only has one frequency in the frequency domain. If it were not harmonically pure, i.e. if it were not sinusoidal, it would be more difficult, if not...

We communicate using sound waves by talking and listening to one another!

yes.

The waves whispered the sounds of the night.