I am the beginning of sorrow, and the end of sickness. You cannot express happiness without me, yet I am in the midst of crosses. I am always in risk, yet never in danger. You may find me in the sun, but I am never out of darkness.
The letter S.
Cái gì luôn ở phía trước bạn, mà bạn không bao giờ nhìn thấy