sanguis

Sanguis, sanguinis, m., third declension. The stem is sanguin-, so the nominative is the odd one out and every other case is longer by a syllable.

Latin keeps two words for blood and the distinction is worth holding on to: sanguis is blood in the veins, the living stuff, and by an easy step it means family and descent, as in eiusdem sanguinis, "of the same stock". Cruor is blood spilled, congealing on the ground, and it is the uglier word. The ecclesiastical corpus leans almost entirely on sanguis, and often on one phrase in particular, sanguis Christi. English took sanguine, consanguineous and sanguinary from it, and French sang comes straight down the line.