What goes up but never comes down?

Which five letter word can be added at the end of below word to form a
valid word?

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

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

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?

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

If you’ve got me, you want to share me; if you share me, you haven’t kept me. What am I?

If a boy blows 18 bubbles,
Then pops 6 eats 7 and then
He pops 5 and blows 1.
How many are left?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

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