A year or so back Carl Zimmer asked the science world if life could be defined in three words.
I don’t think he would have been too concerned if the answer was in four or five or six words, the point of his question, I believe, was that for a definition of life to be useful, it has to be concise, and therefore, simple, understandable.

I proposed that life could be defined in three words – independent spontaneous cooperation – an argument that I first put here at Science 2.0 in early 2009 with What Is Life? and in subsequent variations on the theme in The Problem With Defining Life, Jack Szostak and the Origin of Life, The Intelligence Paradox, and The Language of Life. The question came to the fore again when Gerhard Adam presented What Is Life, Part 2.

Gerhard was never quite convinced by the cooperation explanation of life, but as he was never able to refute it, I assumed that he was being unreasonably negative. Then, in the comment section following his article, just as I thought I was about to convert him, he came up with this; “After thinking about it, perhaps a better word would be synergy.”

 The significance of synergy grew on me over the next half hour or so.
And after just a little research, I found that the influence of synergy in evolutionary studies has been admirably covered by Peter Corning in his 1998 paper, The Synergism Hypothesis. After reading this I had to concede that Gerhard’s gut feeling was right. Cooperation as the explanation of life, even independent spontaneous cooperation, was just a little too brief to cover the matter adequately. Not that the cooperation view is wrong, (cooperation is fundamental to synergy in living systems) it’s just that life has an element of wonder or mystery about it that cooperation alone does not quite satisfy. That element is satisfied by synergy.

So, what is synergy?
1. The interaction of two or more agents or forces so that their combined effect is greater than the sum of their individual effects.
2. Cooperative interaction among groups, especially among the acquired subsidiaries or merged parts of a corporation, that creates an enhanced combined effect.

As that definition shows, synergy can be observed at a non-biological and a biological level, where at the biological level the interaction is cooperation.
So the general sense of the term involves an enhancement effect which, like life itself, seems to come from nowhere.

The effect of toxins on a living organism for example, (while it could hardly be said that they cooperate,) produces an outcome greater than the sum of the individual effects.

In The Synergism Hypothesis Peter Corning used synergism to explain aspects of social behaviour and evolution using extensive examples from the natural world, but he took care to point out that his use of the word was a little more restrained than the version given here, perhaps to avoid criticism that he was overstating his case:
"Synergy" (from the Greek word synergos) is another such umbrella term. Although it is often overlooked, underrated, or misunderstood (or called by a different name), synergy is a ubiquitous and fundamentally important aspect of the natural world. (For an in-depth discussion, see Corning 1983; also 1995, 1996, 1997.) Synergy, broadly defined, refers to combined or "co-operative" effects -- literally, the effects produced by things that "operate together" (parts, elements or individuals). The term is frequently associated with the slogan "the whole is greater than the sum of its parts" ... We prefer to say that the effects produced by wholes are different from what the parts can produce alone.

And yet, it’s the whole (in some cases) being greater than the sum of its parts that highlights the magic of synergy. The magic of the process is an illusion, of course. For example, possibly the most common synergism we see in the natural world is division of labour, a behaviour that has produced huge increases in productivity and security across a wide range of species, (with obvious implications for survival, and therefore evolution) yet this phenomenon was shown to have a mathematical basis in the 19th Century by the economist David Ricardo.

Stunning benefits resulting from synergy are found throughout the biological world, as in the ability of eusocial insects to control nest temperature. This could not be achieved by an individual or a small group, but the cooperative work of many transforms the environment of the brood chamber, ensuring survival of the colony. An extraordinary outcome.

Here’s another example from The Intelligence Paradox where I described a synergistic effect without appreciating its full significance;
The astounding and rapid advances that took place in the 20th Century in the field of genetics were the result of a global sharing of information and hardware among laboratories. This raised level of cooperation effectively equated to a raised level of intelligence as was proved by the results. As soon as one laboratory cooperated with another, the intelligence of the new unit was higher than the sum of the two separate units. And as the number of participating laboratories grew and the cooperation developed, so did the intelligence.
Another extraordinary outcome.

And it’s these extraordinary outcomes that link synergy to an understanding of life itself. (Keep in mind that life is not living entities or their functions. Life is the driver of those functions, the essence of the entities.)

We’ve seen synergy at work in groups of organisms, but it was also present at the origin of life.
When life began, the transition from chemistry to biology was a one-step process. There were steps leading to the crucial point, steps in the gradual increase in complexity of certain molecules and the complexity of their interactions, but once sufficient complexity was reached that the molecules could cooperate in a self-sustaining system, life existed. What was the difference between the self-sustaining system and all previous configurations? The difference was cooperation with an extraordinary outcome. Synergy, in other words. 
So if at one moment we have a lifeless collection of molecules and the next moment we have a living entity, and the only difference between the two is the sudden appearance of synergy, then synergy is life. That difference holds true for all levels of life, as in the example of the genetics laboratories cooperating for extraordinary advances in knowledge. We saw there a collection of laboratories transformed into a living group by the appearance of synergy.

From the point of the origin of life, each step on the path of further development of life forms was characterised by synergy, (1) to the point where it exists all around us to such a degree that we almost fail to see it, (2) and certainly fail to appreciate it fully.

Because we fail to appreciate synergy fully, its outcomes appear wonderful, even mysterious. Life itself seems wonderful and mysterious, but that sense of wonder has not only induced a perception that perhaps life cannot be explained, (3) it has muddied the waters so much that many who consider the matter cannot distinguish between life and life form. (4)

Still not convinced?
Consider Peter Corning’s description of John Maynard Smith’s contribution to the issue.
“Maynard Smith and Szathmáry also make liberal use of the synergy concept in their new volume on the evolution of complexity, The Major Transitions in Evolution (1995). Moreover, their detailed study of the process of biological complexification in evolution is consistent in its overall vision with the more explicit conceptualization in The Synergism Hypothesis. Maynard Smith, in a personal communication, acknowledged that the "universal" significance of synergy became apparent to them only after their book was completed.”

Why does synergy have universal significance? Because, as Corning and Maynard Smith/Szathmary found in separate studies, synergy is found wherever life is found – in cells, in organisms, in groups, in symbioses, in parasitism, in ecologies. But as the functions that we see in all those different levels of living systems vary considerably, the only feature they have in common is life itself.
So life is synergy. A one-word definition of life.

(1) For example, the next stage after the origin of life might have been the ability to replicate, another truly extraordinary outcome.
(2) Groups are a good example of the failure to appreciate synergy and life. We tend to lose sight of the fact that groups are living entities because they perform the functions of living entities – metabolism, homeostasis and reproduction.
(3) In The Social Conquest of Earth, E.O.Wilson said this about the inquiry into what constitutes human nature; “Surely all will agree: a clear definition is the key to understanding the human condition as a whole. But the achievement of that definition it turns out, is an extraordinarily difficult task. Human nature is obvious through its manifestation in everyday life. Its intuitive expression is the substance of the creative arts and the underpinning of the social sciences. Yet its true identity has remained elusive. There may be an emotional, very human reason for this persistent ambiguity. If raw, untransformed human nature were to be revealed, and the philosopher’s stone thus attained, what would it be? What would it look like? Would we love it? A better question might be – do we really want to know? Perhaps most people, including many scholars, would like to keep human nature at least partly in the dark. It is the monster in the fever swamp of public discourse. Its perception is distorted by idiosyncratic personal self-regard and expectation...”
All of those issues apply equally to the question of explaining life. These questions seem to go straight to the emotional side of our nature, preventing reasonable discussion.
(4) Even the remarkably perceptive Peter Corning fell for the language trap in his article What is Life; “So what can we conclude? Life is a phenomenon that has a great many distinctive properties, but many of these in turn are the result of a very long process of invention – of “tinkering” rather than a pre-planned “engineering” project, as the Nobel biologist François Jacob (1977) put it in a much-quoted article in Science. Life, as we observe it and live it, can also be defined in terms of what it is able to do, and what it does. By that definition, the very nature of life has progressively expanded and become more enriched over time with new capabilities – and new synergies. So the final answer to that provocative question, “What is Life?” is that it is still evolving, still creating itself, still exploring its potentialities and still discovering new forms of synergy, along with addressing many ongoing challenges and coping with new threats.”
You’ll notice that in that passage Peter Corning does not mention life forms or organisms at all, yet he is clearly referring to life forms as well as life, alternating between the two under the umbrella term “life”. This confusion must end. It is not life that “invents” and “tinkers” and has “progressively expanded and become more enriched over time” it is life forms that have done that. Life is the process that underlies and drives those outcomes. Peter Corning’s error is all the more remarkable when we consider the subtitle to his What is Life? -  Among Other Things, It’s a Synergistic Effect!
So close, and yet...