logical relationship

A dependency between two project activities, or between a project activity and a milestone. See also precedence relationship. The four possible types of logical relationships are: Finish-to-start: the "from" activity must finish before the "to" activity can start. Finish-to-finish: the "from" activity must finish before the "to" activity can finish. Start-to-start: the "from" activity must start before the "to" activity can start. Start-to-finish: the "from" activity must start before the "to" activity can finish.

SOURCE: apm.org”