Lethargy. Behold one of the most commonly misused words in medicine. Every day, at least once, I will hear “my child is so lethargic” or the reason given for a child’s visit at check-in is “lethargy.”

As Google can attest, the word “lethargy” comes from late Middle English via Old French from late Latin lethargia, from Greek lēthargia, from lēthargos ‘forgetful’, from the base of lanthanesthai ‘forget’. A word with such a rich history should not be misappropriated so widely, and yet here we are.

As much as it frustrates me, I can certainly understand the confusion surrounding the word. There are many words that a have a “layman” explanation that varies significantly from the medical term. Lethargy is certainly not the only example of that.

In layman’s terms, lethargy means “a lack of energy and enthusiasm.” However in medical terms, lethargy means “a pathological state of sleepiness or deep unresponsiveness and inactivity.” Any child that can walk in to an exam room and/or answer questions is, by definition, not lethargic.

Some people may say, is this really something that bothers you that much? And, to that, I can only say: Yes.

But WHY does it bother us in medicine that much?

Perhaps it is because medical care is largely based on making decisions with limited information. My job is to quickly and correctly take the information that is given to me, draw conclusions and connections, and come to a diagnosis. There are simply not enough hours in the day to learn everything about a patient and their symptoms. Medical diagnosis exists in a world of uncertainty. So every word a patient uses to describe their symptoms is important.

To appropriately care for patients, we must take them at their word. And to that end, words matter. Lethargy and “tired” are not synonyms. Perhaps parents want to justify their concerns about their child. Perhaps they truly believe their child is pathologically unresponsive. Or perhaps they have an entirely different rationale for choosing specific words. That is something only that parent can know for sure. But, again, words matter.

We as pediatricians do not think less of the parents that say “my child has been more tired the past few days.” We do not put less thought into caring for those children. I want to make the correct diagnosis.

My internal flow-chart for getting to the right diagnosis is categorically different for the “tired” child and the “lethargic” child. Neither is more important than the other, they simply encompass different things. For example, if you are at a clothing store looking for a pair of pants, you would be wise to not tell the salesperson, “I need a shirt.” Maybe that’s a silly comparison. But I’m a pediatrician, my life is filled with silliness.

In conclusion. Help me help you.