Where does “пятилетний” come from?

пятилетний (Russian) comes from Russian пять, from Old Church Slavonic пѧть, from Proto-Slavic pętь, from Proto-Indo-European pénkʷe — five.

пятилетний (Russian): five-year; five-year-old

Definitions

  1. five-year; five-year-old

Ancestry of “пятилетний”, step by step

пятилетний traces back through two separate lines of ancestry.

via Russian пять

StepLanguageWordMeaning
1Russianпятьfive; second-person singular imperative...
2Old Church Slavonicпѧтьfive
3Proto-Slavicpętьfive
4Proto-Indo-Europeanpénkʷefive

via Russian ле́то

StepLanguageWordMeaning
1Russianле́тоyear; summer, year
2Old East Slavicлѣтоtime
3Proto-Slaviclětosummer; year
4Proto-Indo-Europeanleh₁tóm—
Every word from Proto-Indo-European pénkʷe →Every word from Proto-Slavic pętь →Every word from Old Church Slavonic пѧть →