[lo.cus] n, pl lo.ci [L--more at stall] (1715) 1 a: the place where something is situated or occurs: site, location "was the culture of medicine in the beginning dispersed from a single focus or did it arise in several loci? --S. C. Harvey" b: a center of activity, attention, or concentration "in democracy the ~ of power is in the people --H. G. Rickover"
2: the set of all points whose location is determined by stated conditions
3: the position in a chromosome of a particular gene or allele