In Greek thought, mataios describes anything that fails to achieve its purpose or lacks real substance. Paul uses it to expose the hollowness of worldly reasoning (1 Cor 3:20) and to warn that without the resurrection, faith itself would be futile (1 Cor 15:17). The multilingual evidence is strikingly uniform: Spanish vana, French vain, and German eitel all converge on the same semantic core of emptiness and fruitlessness. In Acts 14:15, Paul and Barnabas urge the Lystrans to turn from 'vain things'—lifeless idols—to the living God, showing the word can characterize entire systems of belief as hollow.