Tài liệu Tính đa dạng của Tiếng anh

To use a language properly, we of course have to know the grammatical structures of the language and their meanings. But we also have to know what forms of language are appropriate for given situations. There is something called “variety labels” such as <AmE> (for American English),<BrE> (for British English),<RP> o Received Pronunciation),<GA> (for General American),<formal>,<informal>,<polite>,<familiar>.These labels are reminders that the English language is not a single language but many languages, each of which belngs to a particular geographical area or to a particular kind of situation.

The “common core”:
Luckily many of the features of English are found in all, or nearly all varieties. General features of this kind belong to the “common core” of the language.
E.g.
(A)words:
1- offspring. formal
2- Children common core
3- Kids informal
It is safest, when in doubt to use the “common core” term; thus children is the word you would want to use most often. But part of “knowing English” is knowing in what circumstances it would be possible to use offspring or kids instead of children.
(B)grammar: