Like names in the languages of most European nations, Ukrainian names have been greatly influenced by Christianity. By the close of the 10th century, when the eastern Slavic tribes who were ancestors to both Russians and Ukrainians accepted Greek Orthodoxy as the state religion, many Greek names had entered the local language. Despite this strong outside influence, however, genuine Slavic names remained in the culture. Since Russia and Ukraine are linguistic as well as geographic neighbors, names of the two nations are similar when written and pronounced, the difference often being a matter of one letter. For instance, where there is a letter "a" in Russian, Ukrainians will say "o," and where there is a hard "g" in Russian, Ukrainians will say "h."