It is very easy for team members, stakeholders or others to get confused over what different terms in your project mean. Some terms in one context can mean something very different in a different context.
For example, some people may refer to “variations” and some people may refer to “changes”. Yet some people may mean that a variation is an approved change, whereas a change is not yet approved. These and many other terms could have formal definitions (such as those defined in the PMBOK – Project Management Book of Knowledge), however many team members may not be aware of these.
Acronyms are often an even bigger issue. Does OD mean the Outside Diameter of a pipe, or does it mean Once Daily? The answer may be obvious in the context of the project, but the team may not know what it means.
Not having these clearly defined leads to wasted time, mistakes and subsequently, extra costs.
If you have variations, changes, etc, use a standard definition for them (from the PMBOK) that anyone entering the project can understand. I think it is best to list a set of definitions at the start of your Project Management Plan (or a similar location), and also a list of acronyms and their meaning.
Any word or acronym that is specific to that project or that industry and that is not very common knowledge should be defined. Don’t just assume that everyone knows what your terminology means.
Make your project definitions and acronym meanings very clear, and put them in an easy to find and easily accessible location for the project team.