What am I?

Until I am measured, I am not known. Yet how you miss me when I have flown! What am I?

related riddles

I am known to be bad luck when you see me in the dark and oh how I hate the rain but one thing is for sure you won’t hear me bark. What am I?

what dose every body use but i don´t use it that much

I go in hard, come out soft. Blow me hard and I’ll make a pop. What am I?