Ne

A positive or pleasant quality that is difficult to define. This French phrase translates to "I don't know what" in English. She had a certain je ne sais quoi that men found quite attractive.

a pleasant quality which you cannot describe or name He's not particularly attractive but he has a certain je ne sais quoi which women find irresistible.

The highest point of excellence, acme. Loosely translated from the Latin for “there is no reason to go further,” the phrase is a synonym of “zenith.” A new car with all the most modern features that any buyer could wish for (or so the manufacturer claims) might be touted as the ne plus ultra of automobiles. Legend has it that “ne plus ultra”—in its literal sense—was inscribed on Gibraltar's Pillars of Hercules as a warning to mariners not to venture, depending on the direction in which they were sailing, into the Atlantic Ocean or the Mediterranean Sea.