I was reading Julian Barnes The Sense of an Ending, when I encountered this line:

And I thought of a cresting wave of water, lit by a moon, rushing past and vanishing upstream, pursued by a band of yelping students whose torch beams crisscrossed in the dark.

I thought for celestial entities like the Earth, the Sun, the Moon, the determiner should be "the", instead of "a"? But I'm sure the author has his reason for using "a". I am just genuinely confused.


This is a common literary construction. The implication is that moons which appear on different nights, or under different weather conditions or in some other way different viewing conditions are in a sense separate things and can be so referred to.

So "a moon" here indicates just the particular occurrence of the moon which is in the sky on this occasion.


  • During World War 2, the British Royal Air Force planned bombing raids on Germany for nights when there might be a bomber's moon - a bright full moon, not obscured by clouds. – Michael Harvey Sep 28 at 10:34

The author is describing an imaginary scene. In actuality, there is no cresting wave lit by the physical moon. He imagines one of the many possible imaginary waves, lit by one of the many possible imaginary moons. Yes, with reference to the Solar System, we refer to "the" sun. But, any arbitrary one of the clestial bodies that are the stars of the Milky Way Galaxy may be called "a sun."

The point is that "the" refers to a specific element in a set or all the elements of a specific set whereas "a" refers to any single element of that set.

Many planets have moons. Some have multiple moons; others like the earth have but one. We say "the moon is full tonight" because implicitly we are defining a class consisting of the earth's moon, which "class" has only one element. "A moon with active volcanoes is rare in the solar system" recognizes that there is more than one moon in the solar system. Similar constructions would apply to an unspecified moon in the Milky Way galaxy or the universe as a whole.

EDIT: As David Siegel says, the construction is being used here as a literary or rhetorical device. To determine the exact effect or effects the author intended might require analysis of the entire work. I can think of at least two possibilities, which are not mutually exclusive.

One relates to memories of an event, and memories differ in details, emotional tone, etc. This is a reference to a memory of an event, and an event that was emotionally meaningful may be remembered many times. So to use the indefinite article implies that the memory mentioned as occurring at the time that "I thought" was merely one of "my" memories of the event and that those multiple recollections emphasize the emotional importance of the event.

A different possible effect relates to generalization. The event recollected was unique. It happened on a particular night to particular people. So the definite article could be used: "the cresting wave ... lit by the moon ... the band of yelping students." If, however, the author wants to imply that the emotional significance of this event is not unique and that the recollection of other events may trigger the same emotional effect in others, then a subtle way to generalize is to use the indefinite article.

My point, however, was not to attempt literary analysis of a book I have not read. I should of course have referenced that this is an example of a rhetorical device. But my point was that the rhetorical device merely utilizes the "rules" for use of the definite and indefinite articles. It is not just a literary device.

The indefinite article implies that the specific identity does not matter and that there is more than one. We say "the moon" when we are talking about the earth's moon as a unique physical object, but we may say "a full moon" when we are talking about the recurring appearance of that singular physical object. The "rule" you referenced about celestial objects does not exist. The rule is about implicit framing of sets.

Now this takes me back to the literary effect of your example. Here the reference is to a unique event, but the use of the indefinite article affects our perception. Waves are common; the moon appears millennium after millennium, and bands of students have been jeering probably since the first teacher gathered the very first group of students. But "I thought" about a unique concatenation of those banalities. The normal rules of grammar are stretched; the unique event concatenates elements, none of which is even rare; the unique event may elicit an emotion that is common; the unique event is remembered differently at different times and by different people. The uniqueness of the event is transcended by the use of the indefinite article.

  • I don't think in this case the author was imagining a moon of some other planet in some other solar system, although some authors do that. But the construction 'a moon" was common long before the concept of moons about other planets was thought of. – David Siegel Sep 28 at 4:04
  • I guess it falls on my part to clarify this a bit. Yes, the narrator is calling back to mind a night when he and his friends went to the River Severn in south western England. Since it was a flashback scene, so it makes sense that he uses “a” to refer that specific night when the tide was lit by that night’s moon. But am I right in understanding that if we are not talking about Literature, we use “the moon” generally, as suggested in one of the examples above—the moon is full tonight? – Jocelyn Liu Sep 28 at 4:19
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    @JocelynLiu It doesn't have to be literary. "It was a cold moon." The indefinite article here denotes a special "kind" of moon. – Eddie Kal Sep 28 at 4:25
  • @Eddie Kal Yes, but I strongly suspect that the literary use of this construction goes back well before Galileo, at least to Chaucer and probably even earlier. In any case the concept of multiple moons did not enter common literary usage right away. Of course it is now common in works of SF or works that consider other worlds in some way. – David Siegel Sep 28 at 4:31
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    @David Siegel - "And underneath her feet she had a moon, Waxing it was, and shouldè wanen soon." - Geoffrey Chaucer The Knight's Tale c.1400 ('her' refers to the goddess Diana). Galileo lived from 1564 to 1642. – Michael Harvey Sep 28 at 10:43

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