IPA(key): [pɫəskɐˈsʲtʲej] <span class="searchmatch">плоскосте́й</span> • (ploskostéj) f inan pl genitive plural of пло́скость (plóskostʹ)...
(genitive пло́скости, nominative plural пло́скости, genitive plural <span class="searchmatch">плоскосте́й</span>) (mathematics) plane (flat surface extending infinitely in all directions)...