The preventive maintenance meaning is simple to state and hard to run: work done on equipment at a planned time to stop it failing at an unplanned one. Every site that owns a machine has a version, from the daily walk-round to the annual overhaul, and the phrase is searched by people who have been told to set up a programme and want a definition they can hold the programme to. This page gives one, a preventive maintenance description a technician would recognise on a work order, and settles the preventive or preventative maintenance question, which is a spelling and not a distinction.
A working definition
Preventive maintenance is any task done on an asset before it fails, on a trigger the site chose, to reduce the chance or the consequence of failure. The trigger is a date, a run-hour count, a cycle count or a calendar season. The task is an inspection, a service, an adjustment, a replacement or a test. What makes it preventive is not the task but the timing: the same bearing change is preventive on the interval and reactive after the seizure. The site chooses the trigger, which is why the definition is a decision rather than a fact.
A description a technician would recognise
A preventive work order arrives from the schedule with the asset, the task, the checklist and the interval. The technician does the listed steps, records readings and findings, replaces what the task says to replace, raises a corrective work order for anything found that the task does not cover, and closes the job. The next one is scheduled from the close. On this site's worked example that is 60 such jobs a month across 180 assets, 66 hours, and they are the cheapest hours in the maintenance budget because each was planned.
What it is not
It is not inspecting everything on the register every month, which is over-maintenance. It is not the manual's intervals copied without thought, which is somebody else's strategy. It is not a task that is on the schedule and is never done, which is deferral. And it is not predictive maintenance, which triggers on a measured condition rather than an interval; the two are cousins and this hub keeps to the interval-based one because a schedule is what a CMMS holds.
Preventive or preventative
The same thing. Preventive is the older and more common form in engineering writing and in most software; preventative is common in speech and in British English. Standards bodies and the manuals use preventive. A site can use either, and should use one, because a schedule that calls the same task by two names ends up with two tasks.
Questions people ask about preventive maintenance meaning
Is preventive maintenance the same as scheduled maintenance?
Nearly. Scheduled maintenance is any planned task, which includes preventive work and planned corrective work. Preventive maintenance is the subset whose purpose is to stop a failure.
How do I know if a task is preventive?
If it was triggered by an interval or a condition rather than by a failure, it is preventive or predictive. If the asset had already failed, the same work is reactive.
Does every asset need preventive maintenance?
No. Assets whose failure has no consequence and cannot be predicted are better run to failure with a spare. Preventive work is for the assets where the failure costs more than the task.