What does HY stand for?

Honey Yellow

Hydrazine

 A rocket fuel which burns spontaneously with nitric acid or nitrogen tetroxide. Can also be used as a mono-propellant when passed through an iridium-bearing catalyst, it decomposes at high temperature into constituent gases of ammonia, nitrogen and hydrogen. Used in small thrusters for orbit modification and attitude control of spacecraft.

Hygromycin

Hyman

Hyper

Hypericin

Hypermetropia

Hypermetropia is a defect of eye in which near objects arc not distinctly visible. This is also called long-sightedness.

Hydrophobic

Lacking affinity for water: incapable of uniting or mixing with water.  OR A nonpolar molecule or group that has little affinity for water. Hydrophobic groups on molecules in solution tend to turn in on themselves or clump together with other hydrophobic groups because they are unable to disrupt the network of strong hydrogen bonds in the water around them. OR Nonpolar; describing molecules or groups that are insoluble in water. OR From the greek words for water (something like hydro) and fear (something like phobos). A compound is hydrophobic if it is "hates" water and will not dissolve in it. Having little hydrogen bonding capacity and no charge makes a molecule hydrophobic. Most organic molecules, such as hexane, triolein, andstyrene are hydrophobic. Opposite of hydrophilic. Nothing to do with rabies (hydrophobia). OR Preferring not to be in contact with water, as is the case with the hydrocarbon portion of a fatty acid or phospholipid chain. OR Refers to non-polar molecules that have little affinity for water. OR Something that is afraid or repulsed by water. The term is also used to describe portions of molecules that do not dissolve well in polar water molecules. "Hydro" means water. "Phobic" means to be afraid of or dislike. 

Hypothalamus

The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland.