I was recently called a grammar Nazi because I corrected a friend for using an adjective as an adverb. I take that to be a compliment. In this particular case, the error was not all that serious because the meaning was clear even with the error, but, of course, that is not always the case. I was not really trying for a “gotcha” either, though it may have appeared to be one. (If so, I apologize.)
The real point was not even the actual grammatical error. It was something else. I have noticed over the last several years an increasing blurring of the difference between our formal use of English and our informal use, and that bothers me. Formal English, which is what most writers (except, perhaps fiction writers and poets) use has very strict rules (grammar) and usages (diction). These rules are important and are not arbitrary and easily dispensed with. They are essential to the facilitation of communication because they make meanings clear and unambiguous.
Informal English relaxes these rules, which is useful in day-to-day speech where such rigor and clarity are not important. For example, informal English permits the occasional in-fix (the insertion of a word or syllable within a word), as in the split infinitive, or the double negative. There are even words that are acceptable in informal English that are not acceptable in formal English, for example “ain’t”.
Why is the difference important? Language is a very complex thing, and there is more to it than just grammar and vocabulary. There is also tone. I do not mean tone as in musical pitch and timbre. I mean tone as in that which conveys context, importance, solemnity, and so on. Tone is the difference between a speech and a lecture. Formal and informal English carry very different tones, and the confusion of them results far more often than is healthy in confusion of meaning.
To be sure, the distinction between formal and informal English is not and should not be a hard and fast one. The ability of one to absorb usages from the other is one of the ways in which language changes over time. There was a time when contractions were rare in formal English though common in informal English. It appears to me, though, that the boundary has become so porous in recent years that there is a danger of confusing the one for the other, with the result that formal English could become so attenuated as to nearly disappear. And that would be a grave loss.
Or so I think.