The first thing that comes in the mind when you hear the word "SECOND" is time. Actually second is the unit of Time and is used worldwide. Under the International System of Units, the second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom. But the word second is used in many context. It is referred to a Runner up in any sports, events, etc. It can be used to refer old bikes, cars, automobiles, mobiles and many more things. A new thing has been recently introduced internationally is a "Leap Second" after leap year.