The act of speaking, or singing, in a language incomprehensible to the speaker and the audience, familiar in times of intense religious emotion in Christian and non-Christian communities. It was experienced at Corinth (1 Cor. 12: 10) but Paul advised the Church not to stress this particular gift, also known by the term glossolalia. Love was the greatest gift, not the display of ecstatic utterance.

The events in the Upper Room at Pentecost (Acts 2) when the Spirit empowered the apostles, as also perhaps at Ephesus when Paul laid his hands on some converts (Acts 19: 6), suggest that the utterances were in foreign speech intelligible to the natives of those regions. There is evidence that at the end of the 17th cent. CE persecuted Huguenots in France spoke in foreign languages; but modern linguistic scholars have shown that the utterances spoken in tongues do not meet the criteria of what constitutes a natural human language.