So what is the difference between a moving van and a moving van? The more impatient among us will say, “Well, exactly nothing, because you’ve only said the same thing twice,” while the more grammatical might suspect a clue in the suffix –ing. I’d go with the grammarians.
This seemingly idle question illustrates in fact the difference between what grammatical science calls a participle and a gerund. The very term participle may echo forth terrors from English class years ago, but although a cunning beast, it can be captured and tamed. It’s always best to begin, I’ve learned, with understanding why something is called what it is called. The term participle derives from the Latin for sharing, or better, something like taking a part of itself (the letters part we can see in the word mean just that, a part or portion). A participle, then, is a linguistic device that takes part of itself from a verb and part from an adjective, and it is summarily defined as a verbal adjective.
There are a number of participles in English grammar (of course), but the one in question here is called the present participle, and present participles always end in the suffix –ing. Adjectives, as we know, describe nouns, and so if we regard moving as a participle in the phrase a moving van, then the meaning is a van that is moving—down the road or across the parking lot, perhaps with a good lot of your belongings in it. Reading the phrase with some attention, you can sense mentally a degree of action in an otherwise simple description, and that’s because of the fact that participles are built in part from verbs, here the verb move.
But, strange to say, actions can become things. If I say that moving is such a chore, even a quick and simple analysis of that clause shows that moving is not describing anything; it is, instead, naming something, that aggregation of a thousand and one little actions which all together comprise what we call moving, the transferring of one’s possessions from here to there. And when a word names something, that word is a noun. But we’ve just agreed that moving is a participle, and therefore an adjective. So what’s going on?
The suffix –ing forms not only the present participle, a verbal adjective, but also what is called a gerund, a verbal noun. Like the participle, a gerund is built from a verb (the term derives from the Latin gero, to carry), but instead of describing a noun, which is what a participle does, the gerund is a noun. So if we now construe moving in the phrase a moving van as a gerund, the phrase can also be read to mean a van for moving. You can hear the difference between moving as a participle or a gerund in the way we pronounce the phrase. If we mean to describe a van that is moving down the road, we will accent the noun: a moving ván; but if we mean a van that is used for moving, we will accent both nouns: a móving ván. You may object and say that even as a gerund, moving is still describing van, but you would be forgetting that nouns are often derivatively employed as adjectives, and here the two together almost make a compound noun (all of which constitutes a grammatical topic which, like the sleeping dog, it is probably better to let lie for now).
There is no writing of English without the use of participles and gerunds, and understanding a little of the technicalities of the two can suggest alternatives in our revision work (for example, I could have just written without using participles instead of without the use of participles and saved myself two words). The whole topic repays close attention, such is the subtlety of our minds in the world.