What am I?

What can always be measured but never can be seen?

related riddles

When I’m first said, I’m quite mysterious, but when I’m explained, I’m nothing serious. What am I?

I have a hundred legs, but cannot stand. I have a long neck, but no head. I cannot see, and I help keep your house neat and tidy. What am I?

I am enjoyed with a pot and some pointy sticks. What am I?