The swan was seen as a traditional symbol of beauty and grace in ancient Greece, and was sacred to Aphrodite. The swan was also sacred to Apollo, the god of music (among other things), in Greek mythology. At the time, the people believed that the swan sang a sweet and beautiful song when people died.
For example, in case of monatomic gas it is just a kinetic energy of motion of atoms of gas as measured in the reference frame of the center of mass of gas. In case of molecules in the gas rotational and vibrational energy is involved.
Energy occurs in many forms, including chemical energy, thermal energy, electromagnetic radiation, gravitational energy, electric energy, elastic energy, nuclear energy, and rest energy. These can be categorized in two main classes: potential energy and kinetic energy. Kinetic energy is the movement energy of an object. Kinetic energy can be transferred between objects and transformed into other kinds of energy.