Her smile is very natural, and it feels comfortable.

In philosophy, natural law refers to the moral laws of the universe.

My biological clock is disrupted, and I've been having sleepless nights.

The equilibrium length of this spring is 5 centimeters.

He prefers natural foods.

This wood may spontaneously combust if the humidity is high.

His car spontaneously combusted all of a sudden.

Natural rights are rights that humans have from birth.

Invasive species can have a major impact on the natural environment.

Weak interaction is one of the four fundamental forces between elementary particles.