The word locus (plural loci) is Latin for "place".
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 homozygous (have the same allele at a locus) or heterozygous (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.
Locus is a science fiction newszine. See: Locus (magazine)