A fraction of a second denotes an incredibly short amount of time. There are several synonyms for this term, including "instant," "moment," and "split-second." The term "blink of an eye" is also used to refer to a fraction of a second, highlighting how quickly things can happen. Another synonym is "microsecond," which is one millionth of a second. The term "nanno-second" is another synonym for a fraction of a second. This is an even shorter period of time as it refers to a billionth of a second. These synonyms are often used in fields such as science, sports, and military, where quick reflexes and precision are essential.