Answer:
In the night a mountain, in the morning a meadow.
My life can be measured in hours. I serve by being devoured. Thin, I am quick. Fat, I am slow. Wind is my foe.
He has one and a person has two. A citizen has three. And a human being has four. A personality has five. And an inhabitant of earth has six.
Metal or bone I may be, many teeth I have and always bared. Yet my bite harms no one. And ladies delight in my touch.
Take one out and scratch my head I am now black but once was red.
What language does a billboard speak?