(a.), a technical term in a number of different disciplines.

1. In astronomy.

Here it corresponds to Gr. διάμετρος, in the Almagest άχρόνυκτος, Lat. oppositio, the term for the opposition of a planet and the sun or of two planets with one another. In opposition, the difference in longitude between the two heavenly bodies is 180°; while the modern use is to take no note of the deviations of latitude from the ecliptic, al-Battānī expressly emphasises ( Opus astronomicum, ed. Nallino, iii, 196) that we can only have the true muḳābala when both bodies are either in the ecliptic itself or…