Gantt Chart Glossary: 100 Key Terms Every Project Manager Must Know
- Michelle M
- 3 days ago
- 8 min read
Gantt charts are one of the most powerful and widely used tools in project management. They give a clear, visual representation of tasks, schedules, dependencies, and progress, helping project managers plan, monitor, and control projects efficiently. By displaying activities along a timeline, Gantt charts simplify complex projects and align teams toward shared goals. However, to truly master them, it is essential to understand the vocabulary surrounding Gantt charts.
This Gantt Chart Glossary includes 100 important terms, each explained in detail, so that project managers, stakeholders, and teams can navigate project schedules with confidence. Whether you are new to project management or a seasoned professional, this resource will help you speak the language of Gantt charts fluently.
1. Gantt Chart
A Gantt chart is a visual project scheduling tool that displays tasks on a timeline. Each task is represented by a horizontal bar spanning its start and end dates. It helps teams coordinate and track progress effectively.
2. Task Bar
A task bar is the rectangular bar on a Gantt chart representing the duration of a task. The position shows start and finish dates, while the length reflects the time allocated.
3. Milestone
Milestones are significant points in a project, often marking the completion of key deliverables. They are usually displayed as diamonds instead of bars on Gantt charts.
4. Dependency
A dependency links two tasks, showing that one relies on the start or finish of another. Arrows connect these tasks to visualize the sequence.
5. Critical Path
The critical path is the longest chain of dependent tasks that determines the project’s finish date. Delays in critical path tasks delay the entire project.
6. Baseline
A baseline is the approved plan of tasks, dates, and costs used to track progress. It allows managers to compare actual performance against planned schedules.
7. Progress Bar
Progress bars fill within task bars to show percentage completion. They provide stakeholders with a quick overview of status.
8. Start Date
The start date indicates when a task begins. It is shown as the left edge of a task bar on the Gantt chart.
9. Finish Date
The finish date is when a task should be completed. This is represented by the right edge of the task bar.
10. Duration
Duration refers to the total amount of working time required to complete a task. It determines the length of the task bar.
11. Slack Time
Slack time, or float, is the extra time a task can be delayed without affecting subsequent tasks or the project’s finish date.
12. Lead Time
Lead time allows a successor task to start before the predecessor finishes. It accelerates task overlap to shorten project duration.
13. Lag Time
Lag time is the intentional waiting period inserted between dependent tasks. For example, waiting for paint to dry before applying another coat.
14. Task Hierarchy
Task hierarchy organizes tasks into parent and child tasks, making complex projects easier to manage. Parent tasks summarize groups of subtasks.
15. Subtask
A subtask is a smaller unit within a parent task. Subtasks break down complex work into manageable pieces.
16. Task ID
A task ID is a unique identifier assigned to each task. It makes it easier to reference and track tasks.
17. Resource Assignment
Resource assignment links people, equipment, or materials to tasks. It clarifies who is responsible for completing each activity.
18. Over-allocation
Over-allocation occurs when a resource is assigned more work than they can complete in the time available. Gantt charts highlight this issue for correction.
19. Timeline View
The timeline view is the horizontal calendar at the top of a Gantt chart. It shows days, weeks, or months depending on project scope.
20. Calendar Scale
The calendar scale adjusts the level of time detail displayed. It can zoom in to daily activities or zoom out to months or years.
21. Work Breakdown Structure (WBS)
The WBS is a hierarchical breakdown of all project work. Gantt charts often align with WBS codes to organize tasks.
22. Predecessor Task
A predecessor is a task that must start or finish before another task can proceed. It dictates sequence.
23. Successor Task
A successor is a task that follows and depends on a predecessor. Its schedule is tied to the earlier task’s progress.
24. Finish-to-Start (FS)
The most common dependency where the successor cannot start until the predecessor finishes.
25. Start-to-Start (SS)
This dependency means the successor cannot start until the predecessor has started. Both can run in parallel once triggered.
26. Finish-to-Finish (FF)
This dependency type requires the successor to finish only after the predecessor has finished.
27. Start-to-Finish (SF)
A rare relationship where the predecessor cannot finish until the successor starts.
28. Task Constraints
Constraints limit scheduling flexibility, such as “must start on” or “must finish by” dates.
29. Fixed Duration
A task set with fixed duration will always take the specified amount of time regardless of resource changes.
30. Effort-Driven Task
Effort-driven tasks adjust their duration based on resource availability. Adding more workers can shorten completion time.
31. Baseline Variance
Baseline variance measures the difference between planned dates and actual performance. It reveals scheduling gaps.
32. Gantt Chart Legend
The legend explains symbols, colors, and notations, ensuring viewers understand the chart.
33. Resource Leveling
Resource leveling resolves conflicts by adjusting task schedules to balance workloads without overloading individuals.
34. Timeline Marker
Markers highlight important dates, such as deadlines, holidays, or phase completions, along the chart timeline.
35. Project Phase
Phases divide a project into logical stages. Gantt charts often group tasks by phases for better control.
36. Deliverable
A deliverable is a product, service, or result produced from tasks. Milestones may represent key deliverables on a Gantt chart.
37. Dependency Arrow
Arrows connect tasks to visualize dependencies, showing sequence and workflow.
38. Task Owner
The task owner is responsible for ensuring the task is completed as planned. Their accountability is clear in assignments.
39. Task Status
Task status shows whether a task is not started, in progress, or complete. Many Gantt tools color-code this.
40. Critical Task
Critical tasks fall on the critical path, meaning delays in these tasks will delay the project’s overall end date.
41. Non-Critical Task
Non-critical tasks have slack and do not immediately impact the project finish date if delayed.
42. Timeline Zoom
Zoom functions allow managers to adjust the time scale for more detailed or broader views of the project.
43. Resource Histogram
A chart linked to Gantt data showing resource workloads over time. It helps avoid overallocation.
44. Task Prioritization
This is the ranking of tasks by importance. Gantt charts visually reflect which tasks are critical to the timeline.
45. Actual Start
The actual start is the real-world date when a task began. It may differ from the planned start.
46. Actual Finish
The actual finish is the real-world date a task was completed. Comparing with planned finish reveals delays.
47. Planned Value
Planned value is the budgeted cost of work scheduled, often aligned with Gantt tasks in earned value management.
48. Earned Value
Earned value is the budgeted cost of work performed, comparing progress against the plan.
49. Work Package
A work package is a group of tasks managed as a unit. Gantt charts often show them as parent tasks.
50. Task Constraints: As Soon As Possible (ASAP)
This constraint schedules tasks to start as soon as conditions allow, without unnecessary delay.
51. Task Constraints: As Late As Possible (ALAP)
This schedules tasks to start as late as possible without delaying successors.
52. Task Constraints: Must Start On (MSO)
This constraint fixes a task to begin on a specific date, overriding flexibility.
53. Task Constraints: Must Finish On (MFO)
This locks a task to finish on a specific date, regardless of dependencies.
54. Task Constraints: Start No Earlier Than (SNET)
This prevents a task from starting before a specified date.
55. Task Constraints: Finish No Later Than (FNLT)
This ensures a task finishes before or on a specified date.
56. Resource Calendar
A resource calendar shows availability, accounting for vacations, weekends, or holidays. It informs task scheduling.
57. Project Calendar
The project calendar defines working days, shifts, and holidays for all tasks.
58. Baseline Schedule
The approved schedule baseline is used for monitoring performance against the original plan.
59. Task Rescheduling
Rescheduling adjusts task dates to reflect progress, delays, or new constraints.
60. Gantt Chart View
The Gantt view is the graphical portion of scheduling software displaying bars, dependencies, and milestones.
61. Timeline Alignment
Ensures tasks are aligned with dependencies and logical sequencing in the Gantt chart.
62. Task Dependencies: Hard Logic
Hard logic dependencies cannot be altered, such as pouring foundation before building walls.
63. Task Dependencies: Soft Logic
Soft logic reflects managerial preferences but could be changed if needed.
64. Resource Dependency
When tasks depend on the availability of shared resources, shown in adjusted schedules.
65. Task Splitting
Splitting divides a task into segments separated by idle time.
66. Tracking Gantt
A Tracking Gantt is a version of the chart showing both planned and actual progress side by side.
67. Task Drift
Drift refers to gradual slippage of tasks against the baseline.
68. Milestone Slippage
When a milestone is completed later than scheduled, affecting progress reports.
69. Forecast Finish
A predicted finish date based on current progress trends.
70. Resource Contour
Resource contours shape resource usage over time, such as front-loaded or back-loaded workloads.
71. Task Effort
The estimated total work hours needed for a task, separate from duration.
72. Float: Free Float
Free float is the time a task can slip without delaying successors.
73. Float: Total Float
Total float is the time a task can slip without delaying the project finish.
74. Slack vs. Float
Both terms describe scheduling flexibility. Slack is commonly used interchangeably with float.
75. Overlapping Tasks
Tasks that run simultaneously on the Gantt chart to optimize schedule time.
76. Timeline Compression
Techniques like crashing or fast-tracking to shorten project timelines.
77. Crashing
Adding resources to shorten task duration without changing scope.
78. Fast Tracking
Running tasks in parallel that were originally sequential, increasing risk but saving time.
79. Resource Bottleneck
When a single resource causes delays in dependent tasks.
80. Project Buffer
Extra time added to protect against schedule risk.
81. Feeding Buffer
Time padding added before a task enters the critical path.
82. Management Reserve
Unscheduled time or resources set aside for unforeseen events.
83. Schedule Baseline Freeze
Freezing the baseline prevents further changes, locking a reference point.
84. Task Costing
Assigning costs to tasks, which can be integrated with the Gantt schedule.
85. Cost Baseline
The approved planned budget distributed across tasks and time.
86. Schedule Variance
The difference between planned and actual schedule performance.
87. Percent Complete
A measure of how much of a task is finished, often shown as a progress bar.
88. Work In Progress (WIP)
Tasks currently underway, visible as partially filled task bars.
89. Idle Time
Periods where no work is happening, often gaps between tasks.
90. Resource Availability
Indicates how much time a resource can dedicate to tasks in the schedule.
91. Resource Pool
The collective set of people and equipment available for allocation.
92. Overlapping Milestones
When multiple milestones occur simultaneously on the Gantt chart.
93. Task Criticality Index
Measures the likelihood of a task being on the critical path.
94. Earned Schedule
A method of analyzing schedule performance by comparing earned value to planned schedule.
95. Baseline Shift
When adjustments are made to the baseline to reflect approved changes.
96. Rolling Wave Planning
Progressive elaboration of tasks in near-term detail while keeping future tasks at a high level.
97. Schedule Risk Analysis
Examining uncertainties and their impact on the Gantt schedule.
98. Timeboxing
Allocating fixed time slots to tasks regardless of scope.
99. Resource Allocation Matrix
A chart showing which resources are allocated to which tasks.
100. Project Timeline
The complete chronological sequence of project tasks, milestones, and deliverables represented in the Gantt chart.
Conclusion - Gantt Chart Glossary
Mastering these 100 glossary terms empowers project managers and teams to fully utilize Gantt charts. By understanding each concept, from dependencies to buffers, you can better schedule, monitor, and deliver projects successfully. Gantt charts are more than visuals they are a language of project management, and this glossary helps you speak it fluently.
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