Vanity

Noun

1. That which is vain, futile, or worthless; that which is of no value, use or profit.
2. Excessive pride in or admiration of one's own abilities, appearance, achievements, or possessions.
3. A dressing table used to apply makeup, preen, and coif hair, in which the table is normally quite low and similar to a desk.
4. A washbasin installed into a permanently fixed storage unit, used as an item of bathroom furniture.
5. Any idea, theory or statement that is without foundation.

   "It is a vanity to say that if two stones are dropped from a tower, the heavier will experience the greater acceleration."