the specific site of a particular gene on its chromosome
"Scientists mapped the genetic locus responsible for cystic fibrosis to a specific region on chromosome 7."
the set of all points or lines that satisfy or are determined by specific conditions
"the locus of points equidistant from a given point is a circle"
A place or locality, especially a centre of activity or the scene of a crime.
"The police cordoned off the locus of the accident to gather evidence from witnesses."
In plain English: A locus is simply the exact spot where something happens or exists.
"The doctor searched for the locus of the injury to determine how deep the wound was."
Usage: Use locus to refer specifically to a central point of activity or the exact location where an event occurred rather than just any general area. It is often paired with phrases like "locus standi" in legal contexts, so reserve it for formal discussions about specific sites instead of casual references to places.
The word locus was borrowed into English directly from Latin, where it meant a place or location. It is considered a doublet of the French-derived word lieu, sharing the same original meaning but entering English through different paths.