What am I riddles

I am something to make you think, I am something to make you know. I am something to which the answer you might never know. What am I?

What word in the English language does the following: the first two letters signify a male, the first three letters signify a female, the first four letters signify a great, while the entire world signifies a great woman. What is the word?

If I have it, I don't share it. If I share it, I don't have it. What is it?

When you have me, you feel like sharing me. But, if you do share me, you don't have me. What am i?