Task dependencies represent the order in which tasks must be performed. Dependencies enable you to work out the optimal task order, providing the fastest route through the project. There are 4 types of dependency relationships. A task can have multiple successors or multiple predecessors.

The impact of getting a dependency wrong usually results in delays.  It's important to monitor dependencies throughout the project and communicate them to the project team.

Start-to-start 

Start-to-start diagramPredecessor must start before successor can start.  This relationship allows the Project Manager to run tasks in parallel.

Start-to-finish

Start-to-finish diagramPredecessor must start before Successor can finish

Finish-to-start

Finish-to-start diagramPredecessor must finish before Successor can start.  This is the most commonly used dependency.

Finish-to-finish

Finish-to-finish diagramPredecessor must finish before Successor can finish