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When you set up task dependencies (task dependencies: A relationship between two linked tasks; linked by a dependency between their finish and start dates. There are four kinds of task dependencies: Finish-to-start [FS], Start-to-start [SS], Finish-to-finish [FF], and Start-to-finish [SF].), there may be some successor (successor: A task that cannot start or finish until another task starts or finishes.) tasks that can start before their predecessor (predecessor: A task that must start or finish before another task can start or finish.) tasks are finished, and other successor tasks that cannot be started until after a delay that follows the conclusion of their predecessor tasks:

• Lead time  This is an overlap between two tasks that are linked by a dependency. For example, if a task can start when its predecessor is half finished, you can establish a finish-to-start dependency and specify a lead time of 50% for the successor task. You enter the lead time as a negative value.
• Lag time  This is a delay between two tasks that are linked by a dependency. For example, if there must be a two-day delay between the finish of one task and the start of another, you can establish a finish-to-start dependency and specify two days of lag time for the successor task. You enter the lag time as a positive value. Adding lag time is a way to add slack (slack: The amount of time that a task can slip before it affects another task or the project's finish date. Free slack is how much a task can slip before it delays another task. Total slack is how much a task can slip before it delays the project.) (also called "float" or "buffer") to a task, increasing the amount of time the task can be delayed before it affects the start of another task.

Lead time and lag time can be entered either as a duration (duration: The total span of active working time that is required to complete a task. This is generally the amount of working time from the start to finish of a task, as defined by the project and resource calendar.) (for example, two days after the completion of the task) or as a percentage of the duration of the predecessor task (for example, begin the task when the predecessor's duration is 50% complete).

1. On the View menu, click Gantt Chart.
2. In the Task Name field, select the task for which you want to set lead time or lag time, and then click Task Information .
3. Click the Predecessors tab.
4. In the Lag field, type the lead time or lag time that you want, either as a duration or as a percentage of the duration of the predecessor task:
   • To enter lead time, type either a negative number or a negative percentage (such as -2d for two days of lead time).
   • To enter lag time, type either a positive number or a positive percentage (such as 50% for half of the predecessor task's duration in lag time).

  Notes  

• You can set lead time or lag time between a maximum of two tasks, and the lead or lag time must be set after a dependency is created between those tasks.
• You can quickly add lead time or lag time to a successor task by double-clicking the link line on the Gantt Chart view and then typing the amount or percentage of lead time or lag time in the Lag field.

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