To define “Time” in ten words or less

We can all define time. We all understand what it is and how it works, right? The challenge: to define time in ten words or less.

The Oxford English Dictionary summarise time pretty well:


Pronunciation: /tʌɪm/ noun 1 [mass noun] the indefinite continued progress of existence and events in the past, present, and future regarded as a whole

That’s exactly what I would have said.

The concept is straightforward for anyone who has existed in it. “The indefinite continued progress of existence”, as soon as you get past trying to understand “indefinite”. The continued progress of existence is something we have all related to and seen. But “indefinite” like “infinite” is a concept that we can’t see or experience, as nothing that exists within our own individual line of vision is not definite. Except for time.

OK, but the “past, present and future” are straightforward to understand as long as you live in a world where time exists. Our memories and the memories of others that are recounted to us through historical account are the “past”. So “past” is simple. As long as you don’t think back further than history records, to the Big Bang, when time as we understand it began. But having a finite point in the past means that time is not indefinite, at least in one direction. Still, there is nothing to say that time did not exist previous to the Big Bang, but there are still questions unanswered.

The present exists though. We are all sure of that. You are reading this post in the present. Or, rather, the word you are reading as you are reading it is being read in the present. Because the parts that you have already read have fallen into the past, and the part that you will read if you are polite enough to sustain the rest of this post is the future. So the present exists between the past and the future. For a moment, as in the idea of “now”. but “now” has already passed by the time that you realise it is “now”. And apparently we experience everything 80 milliseconds after it has happened due to the delay in signals getting to our brains, so what you are actually experiencing is slightly in the past, and what is happening now has not happened for you yet…

OK, we’ll jump to the future. No problem. The things that will happen. The future certainly exists. We know that time will continue on to an indefinite point. Unless it stops. Which we would never know about, because it would happen in the future. Or, rather, it would happen in the present, at a moment, but that moment exists in the future.

This is getting polluted. Let’s try another definition; one of something more rational than language. How about science:

“Absolute, true, and mathematical time, in and of itself and of its own nature, without reference to anything external, flows uniformly and by another name is called duration. Relative, apparent, and common time is any sensible and external measure (precise or imprecise) of duration by means of motion; such a measure – for example, an hour, a day, a month, a year – is commonly used instead of true time.”

Sir Isaac Newton, Philosophae Naturalis Principia Mathematica

Newton had an understanding of absolution, and time to Newton was something which existed in an almost physical way. Newton divided time into two separate forms – one of absolution, i.e. “Absolute Time”, the second of relativity, relating to the individual, i.e. “Relative Time”

Absolute Time is something that exists without human perception. This moves perpetually through the universe. It exists and always will exist. It travels and passes, and everything that has happened has happened, and everything that is going to happen is going to happen. To Newton Absolute Time could not be perceived, but it could be inferred through mathematics. For example, the movement of moons around planets show the passing of time, because their movement suggests something calculable has changed and the change in position could not exist without time. So Absolute Time is the constant existence of movement of anything in the universe, but it is imperceptible. Got that?

Relative Time, in contrast, is time that the individual can experience. We know that time has passed by our own perception of things that have happened, and by experiencing the very short-lived present. But relative time is unique to the individual who experiences it. A good metaphor recounted on BBC’s superb radio show In Our Time With Melvyn Bragg. In an episode entitled The Physics of Time speaker and theoretical physicist Jim Al-Khalili suggests that for two football fans at a match cheering on a their winning and losing side respectively, time moves much faster for the losing fan who is hoping for a goal, where time moves slowly for the winning fan who is nervous about conceding one.

So Absolute Time just exists, and we have to believe it despite never experiencing it. And relative time certainly exists but it is different for each one of us. And this was accepted until Einstein threw a spanner in the works in the 1920s and denied that Absolute Time was a unique entity from space, showing that space and time existed and reacted together.

And space and time combined brings me to philosophy for definition number 3:

“Time is not an empirical concept that is somehow drawn from experience. For simultaneity or succession would not themselves come into perception if the representation of time did not ground them a priori. Only under its presuppositions can one represent that several things exist at one and the same time or at different times.”

Immanuel Kant, Critique of Pure Reason

Now we’re getting somewhere. Aren’t we?

OK, Time is not an empirical concept, i.e. time is not relative, or concerned with individual observation. Rather, time is a theoretical thing which exists absolutely. For Kant nothing could exist if time didn’t exist, so we are back to something closer to Newton’s Absolute Time, which we remember Einstein equated to be relational to space. To Kant time is a priori, which in philosophy is a type of dual-knowledge or argument, concerned with space. Kant like Einstein saw time as fully relational to space, and argued that both are elements that we use to structure our experience.

That is to say our own individual experience.

Which is relative depending on whether your team is winning or losing.

And which changes depending on your views of history. And which can be distorted by your predictions of the future. Which is something that has not existed yet, while the present exists and the past once existed but only for a moment and that fleeting moment burned out as soon as the present subsided and a new future was entered into, and became the present, to soon become the past.


And at this point I have only delved into more populist theories of time. We’ve still got simultaneity and presentism, endurantism and perdurantism, chronology and spacetime, history and eternity and Antiphon the Sophist to cover. I’ll leave that for another post.

We’ll stick with the straightforward definitions we have at hand. Define the three concepts above in ten or fewer words. No problem. Let’s take a little from all three and create a definition:

“Time: A priori of progress of existence without reference to anything.”

Oxford English Dictionary, Sir Isaac Newton and Immanuel Kant

Sound about right? Here’s a treat for taking the time to read this:


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