Why Wine Glass Stem is so long?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

A river should be crossed by a father, a mother and their two sons and two daughters.
There are some rules that should be followed while crossing the river. There can be only two people in the raft while crossing. The daughters cannot be with their father unless there is the presence of the mother. The sons cannot be with their mothers unless the father is present. Unless the guard is on the board, the criminals cannot be with any of the family members. Only the adults like the father, the guard, and the mother knows to use the raft.

How will they cross the river?

Prove that the below maths equation is true.

8 + 8 = 91

People put me on the table and cut me but do not eat me. What am I?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

The answer I give is yes, but what I mean is no. What was the question?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

How can one talk without saying a single word?