Toti. Pluri. Multi.

No these are not the Latin words attributed to Julius Caesar as he warred across Gaul. But in today's battle over stem cells, these prefixes rule.

Why? Human embryonic stem cell research is touted as a potential cure-all for everything from Parkinson's to diabetes. A promise so huge demands words of equal weight and clarity.

Riding to the rescue on the back of the word POTENT are toti (toti-potent),
pluri (pluri-potent) and
multi (multi-potent), which now ricochet around the world with every stem cell headline.

And for good reason.
Toti means whole or entire.
Pluri denotes more.
Multi is another way for saying many.

A totipotent stem cell is one that is capable of generating a complete organism; in other words its potential to become any type of tissue -- including the cells that make up the amniotic sac and the placenta -- is total.

Pluripotent stem cells are everything totipotent cells are MINUS the ability to produce the amniotic sac and the placenta.

Multipotent stem cells, on the other hand, have the ability to become one of the many different types of cells within ONE mature organ, tissue or physiological system.

What does it matter? The answer is simple: precision. Stem cells, a term coined by UCSF researcher Gail Martin in 1981, are not equally potent for all the reasons described. The differences might seem small, but in a political and scientific environment already so highly charged, defining terms disarms the devious or the merely misinformed.

So, too, does knowing that the word totipotent entered the language in 1899. Pluripotent and multipotent emerged during World War I.

Perhaps the lesson is that language and science move faster than armies and that discovery is its own unstoppable force.