From merimna (anxiety, care). Means to be anxious, to worry, to be unduly concerned. Can have a positive sense of genuine care (as Paul's concern for the churches) or a negative sense of sinful anxiety that displaces trust in God.
Jesus repeatedly commanded His followers not to worry about food, clothing, or tomorrow (Matthew 6:25-34). This is one of the most pastorally significant Greek words, addressing the universal human struggle with anxiety. Paul instructs believers to 'be anxious for nothing' (Philippians 4:6), redirecting worry into prayer and thanksgiving. Yet the same word describes Paul's godly concern for the churches (2 Corinthians 11:28), showing that not all care is sinful.