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

What Word am I Looking For ?

Lifeless eyes on my smiling face and watch your child's sleeping place. In their dreams they hold me tight. What am I?

What is the centre of gravity?

What happened when the wheel was invented?

Can you place six X (crosses) in below board without making three in a row in any way ?

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

How many bananas can you eat if your stomach is empty?

A father's child, a mother's child, yet no one's son.

Who am I?

A worker is to perform work for you for seven straight days. In return for his work, you will pay him 1/7th of a bar of gold per day. The worker requires a daily payment of 1/7th of the bar of gold. What and where are the fewest number of cuts to the bar of gold that will allow you to pay him 1/7th each day?