Russian contrasts soft [р'] with hard [р].
Compare
- дурь "foolishness" vs дур (genitive plural of дура "silly woman")
- пар "vapor" vs парь (imperative of "to steam")
- жар "hotness" vs жарь (imperative of "to roast")
- прачка "loundress" vs прячь-ка (imperarative of "to hide")
- праха (genitive of "ashes") vs. пряха "female spinner"
- кор (genitive plural of кора "bark, cortex") vs. корь "measles"
- рад "pleased" vs. ряд "row"