# Learn English – How on Earth can we say ‘a’ moon

indefinite-articles

This question refers to Earth's moon only.

This is really two questions:

1. Our Earth has only one moon. So why and even how can we say 'a' moon?
1b. Restated: What other moon than 'the' moon is in the class of Earth's moons so that I can say 'a' moon? See C) below.

Here is my second question:

Consider the following:
A) There's a fly in my soup.

1. Does the use of the indefinite article restrict a fly to one of a finite number of real flies which have a realistic probability of being in my soup? I know that a generic or prototypical fly cannot be in my soup.

For instance I am in a diner in San Francisco. If I say, There's a fly in my soup, I think I am referring only to one of the 5,000 flies that are in San Francisco. I can't be referring to flies in Los Angeles or flies in Chicago, can I? I can't be referring to fictional flies or flies from outer space either. I can't really be referring to a fly that I saw yesterday, can I? If there are, say, 1 million flies in the world I can only be referring to some subset of that 1 million, not the whole 1 million, because 500,000 are in the Orient and could not possibly be in my soup (a fly from the Orient could be).

In any case, is what is being said the following:

There's a fly in my soup and I don't care to say which one it is, and I don't care which one it is–but I am referring to one of 5,000 flies in San Francisco.

And:

B) There's a full moon in the sky tonight. (Or: There's a full moon out.)
The moon is full once every lunar month. I don't know which lunar month it is. So am I saying:

There's a full moon out tonight and I don't care to say which one it is, and I don't care which one it is–but I am referring to 1 of the 12 or 13 possible full moons?

Last

C) There's a moon in the sky tonight (Or: There's a moon out tonight.)

So am I saying:
There's a moon out tonight and I don't care to say which one it is, and I don't care which one it is–but I am referring to 1 of the 1 that there is circling Earth?

The moons of other planets are not under consideration, because only a geekazoid would know when the moons of other planets are 'visible' from Earth on any given night.

What other moon than 'the' moon is in the class of Earth's moons so that I can say 'a' moon?

You're asking two separate questions. The first one is easy. We say There is a full moon, because there are many full moons, across the course of time. The fact that it could only be one particular full moon on a given day is not relevant.

There is a moon out tonight is a little tougher. Most people would usually say the moon is out tonight. I would argue that in case that the word "a" is used, the moon is actually being viewed in relationship to all the other moons on other nights, as with the full moon. However, the reason for the ambiguity is that all the moons on all the nights are really one object, and we know and accept that fact. This contrasts with the full moons, which are arguably discontinuous and separable, since we're actually referring here to a perceptual phenomenon, not an object.

You might compare There's a moon over Miami tonight. Again we're referring in this case to our perceptions. Of course it's the same celestial object over Miami and over New York. But the experience of perceiving the moon over Miami can be distinguished from the experience of perceiving the moon over New York. It's the same case with your moon spoiling the meteor shower. It's the experience of the moon shining that spoils the show, not the celestial object itself.