The word locus (plural loci) is Latin for "place". It can mean:
- Locus of control, in personality psychology, having an internal or external locus of control
- Locus (genetics), the position of a gene (or other significant sequence) on a chromosome
- Locus (mathematics), the set of points satisfying a particular condition, often forming a curve
- Locus (medicine), the "place" on the body where a pathogen enters
Philosophy, rhetoric, and psychology
- The method of loci is a mnemonic system based on places.
- A Locus (rhetoric) is another name for a literary or rhetorical topos, a method of constructing an argument.
- LOCUS (Level of Care Utilization System), a clinical level of care placement tool for psychiatric and addictions services, developed by the American Association of Community Psychiatrists