glossary — plain english
Milestone
A zero-length moment that matters to people outside the work — a launch, a review, a handoff. On a Gantt chart it's a diamond; in an email it's a date.
Milestones aren't tasks. They have no duration and contain no work — they mark the instant something becomes true: the site is live, the design is approved, the contract is signed. That's why charts draw them as diamonds instead of bars; there's no width to draw.
Their real audience is everyone who isn't doing the work. Executives, clients, and other teams don't plan around your bars — they plan around your diamonds. A good milestone is a moment someone else could put in their own calendar, which also makes milestones the natural place to attach deadlines: "launch by March 28" is a milestone with a date pinned to it, and the plan gets read backward from there.
Ration them. A chart with a diamond every three days has no milestones, just decorated Tuesdays. If it wouldn't be worth an email to someone outside the team, it's not a milestone — it's the end of a task.
See it on a real chart
Describe your project in plain English and ganttchart.ai turns it into a shareable Gantt chart in seconds — every term on this page included. Or read the method first: the plain-English planning guide.