He found her on a dating website.

The ecosystem of this lake is very fragile.

In physics, the inertial frame of reference is a very important concept.

This system is very complex.

He is deeply involved in the study of the meridian system.

Because her immune system is weak, she catches a cold easily.

He loves visual kei bands.

He is an aggressive man in relationships, actively pursuing love.

He is interested in radio wave research.

My nervous system is affected by stress.