Noun
A quartet; -- applied chiefly to instrumental compositions.
Source: Webster's dictionaryThe first to use of the term satellite to describe orbiting bodies was the German astronomer Johannes Kepler in his pamphlet Narratio de Observatis a se quatuor Iouis satellitibus erronibus ("Narration About Four Satellites of Jupiter Observed") in 1610. Source: Internet
These four dignitaries, occupying the four corner stalls in the choir, are called in many of the statutes the quatuor majores personae of the church. Source: Internet
The Four Degrees of Violent Charity, A critical edition of the Latin text is Gervais Dumeige, ed, De quatuor gradibus violentae caritatis, in Ive, Épître à Séverin sur la charité. Source: Internet