My parents English, though tinged with the musicality and characteristic accent of the Caribbean, was always very well spoken, with excellent grammar and vocabulary.

The teacher may describe a rule in the native language to explain a grammatical structure.

Minor proof reading changes have also been made to correct grammar, spelling and punctuation in the texts.

So, a problem in explaining how children learn language, a problem in teaching language to adults so that they don't make grammatical errors, and a problem in programming computers to use language is which verbs go in which constructions.