Answer :
We feel sad about some thing, that happened. Some bad thing happened. So we express our sorrow, and grief. It is an exclamation remark.
There was a cyclone Hudhud which destroyed Visakhapatnam. Alas! the people had to suffer for the next three days.
There was a cyclone Hudhud which destroyed Visakhapatnam. Alas! the people had to suffer for the next three days.