Locus

In biology, a locus describes the position of a gene (or other significant sequence) on a chromosome. A locus can be occupied by any of the alleles of the gene. Diploid or polyploid cells are either homozygote (have the same allele at a locus) or heterozygote (have different alleles at a locus).

In mathematics, a locus is the set of points satisfying a particular condition. It is mostly used when the set of points forms a curve of some sort.