flexible constraint

As opposed to inflexible constraints, flexible ones schedule tasks as follows:

• Finish no earlier than (for projects scheduled from the project's start date).

• Finish no later than (for projects scheduled from the project's finish date).

• Start no earlier than (for projects scheduled from the project's start date).

• Start no later than (for projects scheduled from the project's finish date).

These constraints will not cause schedule conflicts if a task is delayed beyond its constrained date.

SOURCE: microsoftproject glossary-projectlearning.net