The Russian word ‘poltora’ ('1.5') is a remnant of the Old Rus’ counting system
There were other Slavic fractional numerals, but they have not survived in the language.
The Russian language has a unique word ‘poltora’ (‘one and a half’). It was formed from the words ‘pol’ (‘half’) and ‘vtora’ (‘second’). But, it's not the only word like this!
The words ‘poltretya’ (‘half three’, 2.5), ‘polchetverta’ (‘half four’, 3.5), ‘polpyata’ (‘half five’, 4.5) and so on also existed, but simply fell out of use, due to their awkwardness by the 18th-19th centuries. The word ‘poltora’, however, turned out to be more handy in everyday life and easier to pronounce.
