Sinner or Saint?

People commonly call fellow Christians sinners all the time, but rarely are they called saints. Catholics reserve the term saint for a posthumous recognition of one's earthly work. Yet scripture refers to believers on earth as saints. To confuse matters more, the OT definition of sinner was "one found guilty before God," and the NT definition is "to miss the mark and not share in the prize." Since forgiveness of sin and eternal life with God is the Christian prize, how can Christians call a believer a sinner (they're not going to heaven) and still profess them as a fellow believer? It's not paradoxical either. Frankly, it's imposing the English language onto the Hebrew and Greek languages of the Bible which distorts God's message of deliverance. What do you think?