A lot of new terms have entered the health care lexicon—but they don't always mean the same thing to everyone. We have a common vocabulary but not necessarily a common language. We asked Robert Berenson, MD, of the Urban Institute to guest blog on the need for precision.

It's encouraging that so much of the health care conversation in Washington is about delivery system reform, in particular the challenges posed by the intensive and expensive needs of people with multiple chronic diseases. It's also a little disconcerting. We're all talking, but are we talking about the same things?

We need more clarity, more precision.

How are we defining chronic conditions? I have a colleague who says it's like marriage—"It lasts a year or longer. It limits what you can do. It needs care."

Yes, it's funny. But it helps us think about what the definition should be. Under a liberal definition of chronic conditions, by last count I have at least four and fast approaching five, but I would say that I am in excellent health. Is having a certain number of chronic conditions what we're talking about? Or are we talking about those conditions that interfere with our ability to work, to function, to take care of  daily activities? Is it a disease that puts us on a trajectory that will lead to death? Is care management the same thing as care coordination?

Medical homes (which mean very different things to different health system change advocates) can help care for people with chronic conditions. The emphasis on wellness and care coordination, on education and intervention, can help prevent people from developing these conditions, and or can keep people stable and living fairly healthy normal lives for quite some time even when they do develop these diseases.

But what about patients with cognitive deficits and difficulties with the activities of daily living? That's a different category. Can they even, physically, get to their medical home? Or does the medical care have to come to the patient's home? What if a patient has five diseases and is homebound for all intents and purposes but doesn't qualify for home health services under Medicare and isn't on Medicaid?

We also tend to talk about primary care as the focus for care management. But for someone with progressive Parkinson's, the patient will surely be seeing a neurologist as the principal care physician for that condition. Should the neurologist also be the care coordinator or should we be more explicitly defining co-management of patients? Or a nephrologist or a dialysis center where the patient goes three days a week for someone with kidney disease? Most older people with one chronic disease do in fact have others, and their care is complex and demanding.

There is no Holy Grail; we'll probably need different solutions for patients at different points in their disease trajectories. So far, we have not provided rigor to discussions of chronic care coordination, assuming somehow that the same model should apply regardless of which chronic conditions are under consideration. We have a lot to do; it will be easier if we can all agree on what we are talking about.