Vein vs Vane vs Vain Vein (n.) is one of many vessels forming the path for blood returning to the heart; tissue forming the framework of a leaf; a clearly defined stratum of ore, etc. Phlebotomists draw blood by puncturing a vein . Vane (n.) is a blade, fin, or plate on a fan, turbine, etc., that moves or is moved by water, steam or air. A weather vane indicates the direction of the wind . Vain (adj.) excessively proud of one's self; conceited; without real value or importance; worthless; futile. You're so vain, you probably think this example is about you . (Ha! Couldn't resist. :P)