What can you catch but never throw?

It belongs to you, but other people use it more than you do. What is it?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

What is so fragile that saying its name breaks it?

Let's play a word game. Following are some meaningless words that can be completed by adding random letters on either side of the word.

For example, the word "rdo" can be formed into "pardon".

Using the same technique, can you complete the given words?
ecalc
airb
rinci
tibac
uidel
gorit
igna
eyho

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

I have teeth but i don't bite. Who Am I ?

There is something which is always coming but never arrives?

I have eight fingers and two thumbs but I do not live. What Am I?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?