Talking about rules we may come to the use of the word “grammar” in statements like this:
“It is bad grammar to …”
Here the term refers to a way of speaking or writing that is to be either preferred or avoided. Such statements pertain to prescriptive grammar, a set of regulations that are based on what is evaluated as correct or incorrect in the standard varieties. Since we do not have an Academy of the English Language to show the English themselves how their language should be used, there is no one set of regulations that could be considered “authoritative”.
Instead, evaluations are made by self -appointed authorities who, reflecting varying judgments of acceptability and appropriateness, often disagree.
Authorities on USAGE, in this restricted style, primarily deal with disputed usage, a relatively small number of syntactical and lexical items that are controversial within the standard varieties.
Their objections may persuade some to avoid certain usages, at least in their formal writing. Over the last two centuries prescriptive rules have accumulated into a general prescriptive tradition for formal writing that is embodied (with some variation) in school textbooks and student reference handbooks, and in usage guides for general public.
As an occasional consequence of prescriptive pressures , some speakers have mistakenly extended particular prescriptive rules in an attempt to avoid mistakes. A classic instance of such hyper-correction is the use of whom, or between you and I., If he were here
In 1762 Bishop Robert Lowth published his “Short Introduction to English Grammar” Rather than basing his grammatical rules in the usage of the best educated speakers of English, he erringly and foolishly based them on the Latin Grammatical System, a system wholly inappropriate and incapable of dictating usage to a language as different from Latin as Germanic-based English. The result is that many modern usages in English are based upon those false origins.
Some basic prescriptive rules
Do not end a sentence with a preposition.
Do not split the infinitive.
Hot linguistic debate often occurs over a number of normative usage rules. One example which leaps instantly to mind is that “one must never split an infinitive”. In Lowth's grammar infinitives cannot be split because it is not possible in Latin to split the infinitive. Of course not, in Latin it is one word. However, it is not in English. English infinitives are two words. Sometimes it is more logical to split the infinitive - “I cannot bring myself to really like the fellow”
“One must never end a sentence with a preposition”. Again this is a preposterous rule based on the Latin system. But sentences often end with prepositions in English, quite naturally - “What are you complaining about?” It is not right according to prescriptivists. This frustration gave rise to perhaps the most famous quote about grammar of all time, Winston Churchill's comment to his speech writer that the rule “is the sort of bloody nonsense up with which I will not put”. Descriptivists hoped that Churchill's dismissive statement sounded the death knell for the silly rule, but unfortunately it is still a “cherished superstition”, according to H.Fowler, the author of Dictionary of Modern English Usage ( first published in 1926)
Many words have fallen out of regular usage due to senseless prescriptions, which are often based on social judgment. Such a word as ain't. Now ain't seems to be likened to the worst of vulgarisms. But it was as late as the beginning of the 20th century freely used by many upper class educated speakers in the southern part of England and is used today in the casual speech of a good many highly educated southerners and westerners. Some linguists call the situation a “sociological historical accident”. Simply aint developed as a contraction of am not with am not – amn't-aan't – ain't. It also has a second source – have not -hasn't-han't-hain't-ain't. Now these are considered ungrammatical. I am your friend, aren't I?
But the main approach taken in modern grammar books is descriptive. The emphasis is on describing the ways in which speakers and writers of English use the language to communicate with one another, as evidenced in large numbers of spoken and written texts from all over the British English speaking community
It is important that learners should know about some prescriptive rules, about the social importance which attaches to certain prescriptive rules while at the same time they should be aware of the way English is used by real speakers and writers of the language.
Pedagogical Grammar, in its turn, is an approach in linguistics intended to aid in teaching a foreign language. This grammar, this method of teaching is divided into the descriptive – grammatical analysis and prescriptive - the articulation of a set of rules. Pedagogical Grammar requires rules that are definite and coherent.
In other words, pedagogical grammar can be regarded as a description of the grammar of the language made for teaching and learning purposes.