What are the common characteristics of all lipids?

There is only one characteristic that is common to all
lipids, and that is their inability to dissolve in water. They will, however, dissolve
in  a variety of organic solvents, such as benzene, acetone, alcohol, carbon
tetrachloride,and chloroform. This single commonality is generally used to classify
something as a lipid.

Beyond that one charcteristic, lipids
display a wide variety of structures and features. They include oils, fats, and waxes;
they can be liquid or solid at room temperature, and they may have other functional
groups of various kinds attached. One example of this would be the phospholipids that
comprise the majority of the cell membrane. In these membranes, it is the fact that
lipids are chemically incompatible with water that actually helps to create the
structure of the membrane.