What does it mean that the same words mean different things to different people?

Shared vocabulary does not guarantee shared meaning.

Example: Two engineers agree the system needs a better 'architecture.' One means microservices decomposition. The other means cleaner module boundaries within the monolith. They nod along in the meeting, build in opposite directions for two weeks, then discover the divergence in code review. Same word. Different mental models. No one lied or was careless — the word simply activated different meanings in different heads.

Try this: Pick a word you use frequently in your work — 'quality,' 'done,' 'strategy,' 'alignment,' 'simple.' Ask three colleagues to define it in one sentence without discussing it first. Compare the definitions. The divergence will be larger than you expect. Write down the range you discover. You now have evidence that your most common words are less precise than you assumed.