A student asked me recently if he should write a vendor or the vendor in the second sentence of this passage: Our procedure for registering new vendors has changed. If a vendor has completed Form A, they may receive new orders immediately. A minute question, one might say, and the world will not falter on its axis if one overlooks this. But there is something important to see here that can make us more exact and sensitive readers and writers.
First, of course, is the question just what are these words a and the which we use countless times a day. Both are found in association with nouns, the word vendor in our example, and so they are classified grammatically as adjectives; any word that makes a change to, or modifies, a noun is an adjective. We usually think of adjectives, though, as naming some characteristic or feature of a noun (new vendor or reliable vendor, for example), and it is difficult to see at first just what quality of a noun these two adjectives are pointing to. For that reason, they are usually referred to as articles, the word a (or an) called the indefinite article and the called the definite article. The word articulus in Latin means a small joint, something that marks a division or part, like a knot or knuckle, and so referring to these two words as articles points to the fact that, together with their nouns, they form a small section or division of a sentence.
An article is essentially a weaker demonstrative, a word that identifies one thing from many other possible instances of the same thing: that invoice or those customers. We can see best how the articles work by putting them in ascending order of strength with a real demonstrative: a vendor, the vendor, that vendor. The indefinite article points just to the idea of something, the imprecise, generic notion itself: a vendor (as if to say, any particular one you happen to think of, it doesn’t matter). The definite article begins to turn in the direction of something already referred to, but doesn’t go so far as to take its index finger and actually point at it: the vendor (as if to say, the kind of one I mentioned already). And a real demonstrative throws caution to the wind and names names: this or that or these or those vendors.
So to return now to our original question, we can consider our choice between the indefinite and definite article by asking whether anything has already been said about vendor that will have made it more specific; if so, the definite article is then the preferred choice because definite articles refer to something already identified in some way (hence their name definite). The first sentence of the passage refers to new vendors, identifying from the entire number of vendors that the company may work with only those that are new. And that adjective is enough to narrow the reader’s attention when the next sentence refers to vendors again; the condition of having completed Form A applies only to new vendors (not all existing vendors), and so the definite article is the better choice: if the vendor has completed Form A. To use the indefinite article would be to send the reader’s mind into the big wide world of vendors to think of one who has completed Form A, a search that doesn’t need to be made because the vendors we are to think of have already been identified: new vendors. And to go so far as to employ the demonstrative adjective and say that vendor would be to overshoot the mark, to be so precise that the reader wonders which specific one of the new vendors is being referred to.
It’s a subtle point, but there is just no denying that in the arts of reading and writing and speaking (and I would go so far as to say in all the arts), mastery lies in the details. The problem, of course, is that the devil usually lies in the details as well, which is why a little grammatical knowledge can often get us through: for devils cannot withstand the truth.