CANCER, CANCRE, CANCRO. Cancer, the constellation the Crab, is the fourth sign of the zodiac and lies in the northern hemisphere between Leo and Gemini. Hera sent the Crab to help the Hydra when Hercules attacked its several heads. Although the Crab bit his toe, Hercules won the battle. As the moist and cold sign the Crab is the moon's house or mansion (Confessio Amantis VII.1060-1066), the exaltation or sign of maximum power of Jupiter, and the depression or sign of minimum power of Mars (Tetrabiblos I.19).

The moon has passed from the second degree of Taurus into Cancer in four days, MerchT 1885-1889. Phoebus, the sun, is in Gemini, not far from Cancer, his declination, that is, the sun's maximum northern latitude, which it entered on June 12, the summer solstice in Chaucer's time, MerchT 2222-2224, on the day that May meets Damian in the pear tree. Cancer is Jove's exaltation, MerchT 2224. The conjunction of the crescent moon with Saturn and Jupiter in Cancer, the moon's house, causes the downpour of the smoky rain and prevents Criseyde from going home, Tr III.624-626. This astrological conjunction actually occurred on or about May 13, 1385, and is one of the clues for dating the Troilus. When the sun enters Cancer and there is a drought (at the summer solstice on June 12), and the seeds do not sprout from the dry furrows, the sower must look for acorns under oak trees, Bo I, Metr 6. 1-4. According to Ptolemy, this northern declination or latitude is 23 degrees and 50 minutes in Cancer, Astr I.17.1-40. Skeat notes that in Ptolemy's time, the latitude of the sun was 23 degrees and 40 minutes and 23 degrees and 31 minutes in Chaucer's time. Cancer lies directly opposite Capricorn, Astr II.16. The zodiac is divided into two half circles, from the head or beginning of Capricorn to the head or beginning of Cancer, Astr II.16. The head of Cancer is the highest point of the zodiac, and the signs from its head or beginning to the end of Sagittarius are called the signs of right ascension, or "sovereign signs," or "western signs," Astr II.28 31-35. [Ercules: Juno]

Cancer, the English form, appears in medial position, MerchT 2224; Cancre, the French variant, appears in medial position, MerchT 1887, and in the Boece. Both forms appear in A Treatise on the Astrolabe, although Cancer is the preferred form there. Cancro occurs medially in Tr III.625.