Everyday Words Whose Scientific Meanings Are Different


In everyday language, a theory is something that hasn’t been proven. We use it to mean ‘hypothesis’.

I don’t know why socks go missing but I have a  theory.

MARK COLVIN: Do you think that to a degree [the theory of evolution is] a communication failure by science? Do you think that just the very word, “theory”, in the “theory of evolution” has misled people?

RICHARD DAWKINS: Yes, I think that’s not the only communication failure. I think that simply not bothering to go out there and talk in the public square is part of the problem.

from this interview

Here’s how the word ‘theory’ works in scientific literature, compared to some similar words:

  • Hypothesis–> An educated (or uneducated) guess
  • Science Method–> The 7 step process to test said guess
  • Theory–> The “why” of something works
  • Law–> The “what” of something that works

courtesy of Freethought Blogs.


In common usage, ‘natural’ = ‘good’.

The Incredible Arrogance of Thinking ‘Natural’ Means ‘Good’

This one is a marketing difference and it pays to remind oneself regularly: brown packaging and ‘natural’ on the box doesn’t mean jack. Cancer. That, too, is ‘natural’.


A college professor taught me the word “casuistry” when it came up in office hours during a conversation we were having about a presentation I was slated to give on John Donne. It has two definitions: the first more technical definition has something to do with applying abstract rules to concrete instances. The second, in more common usage, is something like “specious, sophistic reasoning.” It’s especially associated with the Jesuits, who (allegedly) used it to rationalize light punishments for aristocratic sinners. It’s a great word. I especially like to use it when I’m losing an argument, because even if, say, my husband is being perfectly logical, nothing undermines a debate by calling him a casuist.



In science, symbiosis means ‘a close relationship’. There are four main kinds of symbiosis, one of which is mutualism.

In everyday English, when people talk about ‘a symbiotic relationship’ we are most often talking about mutualism, or ‘a mutual relationship’. ‘Mutually symbiotic relationship’ would be technically more accurate.

Apart from mutualism,  three other types of symbiosis are:

  1. Commensalism, in which one species benefits while the other remains unaffected
  2. Parasitism, in which one species benefits while the other is harmed
  3. Neutralism, in which both species are unaffected


Common Usage: Man-made chemicals

Scientific Usage: Biologically produced poisons.

(Toxoid: A toxin which has been rendered no longer toxic eg. a vaccination is ‘toxoid’, which doesn’t exactly help the vaccination cause.)


When thinking about the origin of science and philosophy we often show a tendency to underestimate the value of myth. It was critical, rational thinking that replaced the irrational, mythical approach to unknown phenomena. We treat myth as a fable or fairy tale invented by primitive people to recount to their sons and grandsons. However, the story has yet another aspect. There is something unknown, something that transcends our current knowledge and we want to comprehend it, but we are lacking adequate tools to do so. Therefore, we create a myth so that we might at least assimilate this unknown into the realm of our actions. It is true that science and philosophy have converted many myths into rational knowledge, but it is far from true that we no longer use myths.

In some schools of contemporary philosophy the myth concept is still widely employed, but it has evolved into a kind of technical term. Myth in this sense refers to a reality that evades any precise linguistic description. Since this reality cannot be precisely described in our language, it cannot enter into a logical nexus with any linguistic description of our experience. This does not mean that this reality cannot be experienced, but, if it is experienced, it transcends any logically organized linguistic description.

from A Comprehensible Universe: The interplay of Science and Theology


Space and dimension mean different things to physicists and mathematicians than they do to the ordinary person in the street. This is a very hard topic to get your head around if you’re not an astrophysicist, so I’ll leave you with the podcast, a conversation between Ezra Klein and Sean Carroll. They talk about this difference at about the 26 minute mark.


Scientists generally use the term “epidemic” to refer to a disease that occurs suddenly in a discrete population, an outbreak. An epidemic is not declared on the basis of high numbers but on the speed or rate that new cases pop up. In the nineteenth century, the word was used almost exclusively to describe a wave of infectious disease. In the typical graph of an epidemic, the number of cases is plotted against a measurement of time, such as days or weeks, to show how quickly the disease is spreading.

With the notable exception of AIDS, in modern times we’ve had less experience than previous generations with fast-moving infectious diseases, like polio or smallpox, that can affect entire populations. As a result, the time component of the definition of an epidemic has become less crucial. As one consequence, the definition of ‘epidemic’ has broadened. Now, we use the word with little reference to the speed at which new cases are occurring, which puts us one step away from the original usage. And when we talk about epidemics of conditions that are not contagious — such as skin cancer, autism, anorexia nervosa, and teen pregnancy — or conditions and situations that are not even real diseases — like alien abduction, or satanic child abuse — we’re two steps away.

Unstrange Minds: Remapping the World of Autism by Roy Richard Grinker


In everyday English we tend to think of these words synonymously but Covid-19 has put paid to that. New Zealand was one of the first countries saying that they had ‘eliminated’ the virus, which had some people scratching their heads because the virus was clearly still around. There were still a few people in hospital with it, and a few others isolating at home.

Here in Australia, with about the same number of proportional cases, people began to wonder if New Zealand was maybe tooting their own horn by saying the virus had been ‘eliminated’. It was subsequently explained that when virologists say ‘eliminated’ they are saying something specific: Eradication refers to the reduction to zero (or a very low defined target rate) of new cases in a defined geographical area. New Zealand was correct to announce that they had eradicated Covid-19, while also telling New Zealanders that they also weren’t in a position to fully reopen the country and return to normal life.

Elimination is much more difficult. We’ll be able to say Covid-19 has been ‘eliminated’ after the complete and permanent worldwide reduction to zero new cases after deliberate efforts.


You could argue that ‘heritability’ isn’t exactly an everyday English word, but any English speaker would hear it and know it relates to the word ‘heredity’.

Generalists still tend to focus on a binary of ‘nature vs nurture’, a concept that should be retired. Geneticists are now very clear that nature and nurture are constantly interacting with each other. Therefore, the meaning of heritability is more specific than the generalist might assume.

Many features of humans have been shaped by culture, so things like the way tools and fire have shaped our hands and our intestines and our digestive systems. And then I think a lot of our big brains expanded as a response of having to learn lots of cultural information about how to make tools and shelters and arrow poisons and things like that, so this complex body of knowledge that transmits non-genetically. In many ways, I think our brains have evolved to be good at acquiring all that information. … we have to get beyond this kind of dualistic way of thinking, where there’s genetic things that we think of as biological and then there’s cultural learned things which seem to be almost ethereal. When we learn culture, that wires things into our brains … whether we’re learning a language or we’re learning to juggle, if we’re learning the complexity of streets in London, we know that this alters, for example, our hippocampus. And so you get physical changes in the sub-structure, which means that cultural evolution is a kind of biological evolution. It’s just not a kind of genetic evolution.

Joe Henrich

Heritability is a ‘descriptive statistic’. Like all descriptive statistics, it can change in populations over time. This heritability statistic describes the extent to which differences that we observe in a trait (e.g. propensity to alcoholism) are due to inherited DNA differences between people, in a certain population at a certain time.

Generalists mistakenly confuse what is with what could be. Heritability describes the extent to which people differ in propensity to alcoholism, and to what extent that is due to availability to alcohol etc. vs inherited DNA differences.

Another caveat about heritability: Geneticists can only work within the range that they are able to study. This typically covers about 95% of a population but doesn’t include the extremes e.g. single gene mutations, nor does it include the environmental extremes e.g. abuse/neglect.

In short, the descriptive statistic of heritability is not fate.


There’s a tendency to casually conflate ‘Christianity’ with ‘Western’. In the modern world, 90% of Christians are cultural descendants of this Western European tradition, but that leaves 10% who have a non-Western European background.

the branch of Christianity that eventually evolved into the Roman Catholic church was just one branch among many:

  • Syrian Christians
  • Armenian Christians
  • Ethiopian Christians
  • Chaldean Christians
  • etc.

The branch connected to the Catholic church exploded in size, so this dominates much of our thinking around Christianity today. This Roman Catholic branch of Christianity changed many aspects of family:

  • Banned marriage between cousins (and other family members)
  • Preferred neolocal residence (a type of post-marital residence in which a newly married couple resides separately from both the husband’s natal household and the wife’s natal household).
  • Tried to end arranged marriages

All this had the unintended consequence of creating monogamous nuclear families. (Unintended because the church was simply enforcing what it believed God wanted; small families weren’t the aim.) This is what we tend to associate with Christian morality today.


What scientists say in research papers vs. What they actually mean, from io9

This blog is all about narrative theory, storytelling and literature. A few words used differently by specialists in this area, compared to how they are understood by ‘the man on the street’: surrealism and melodrama.