Which way is the best way for to teach English Language Grammar: inductive approach or deductive approach?and why?
I believe Grammar should be taught using the inductive approach. The English language is a complex language and doesn't always follow all the rules, so there's certain things you have to learn in certain ways and it can't be left to chance (deduction), or to the premise that it can be figured out on our own.
Inductive teaching gives set guidelines and principles that must be mastered to achieve the knowlege desired. Grammar is Grammar and pretty much the same whether you're six or sixteen. The only difference is that the primary basics are given to a six-year-old, whereas a sixteen-year-old has expanded the basics through the years, added in writing skills, and developed a larger vocabulary.
A preposition is still a preposition--now there's more of them. A verb is still a verb--only now there's more than one way to conjugate it. A noun is still a noun, and now we've thrown in pronouns. An adjective is still an adjective, but there's all different kinds. An adverb is still an adverb, and it doesn't always end with -ly. The list goes on!
Grammar is like Math, in that each year the same things are taught, only a little more advanced than the year before. It uses repetition, repetition, repetition! Every so often, new material is added, but the same processes and functions are still there, only more advanced. As our minds and capacities grow, so does our comprehension of things.
Grammar is a tool to be used to help us master our language, communicate with each other, and find out about the world around us. If we start out right (induction) and continue steadfast in it, we'll come to the point in our lives where we can start using reasoning (deduction) to help us learn other things!
Children learn the basics of language deductively. They understand (without knowing the terminology or how to express it) that subjects come before verbs, that verbs are conjugated in a regular way, and the syntax of various types of sentences follows a pattern. Once they get to school, though, there's a need to refine those understandings by induction. They need to know the rules before they can grasp the exceptions, and they will need more than a deductive understanding of grammar if they're ever going to learn a foreign language. They might get by with an intuitive grasp of their own language, but that will never work if they're starting from scratch with a new language. Not teaching the rules is doing a disservice to our students.
I use a text called Daily Grammar Practice. This uses the same sentence every day for a week. Monday addresses the parts of speech for the sentence. Tuesday addresses the sentence parts. Wednesday addresses the clause(s) and sentence types. Thursday addresses capitalization. Friday addresses diagramming. Other mini-lessons are embedded in the sentence, and this arrangement is wonderful because each day builds on and reinforces the learning from the previous days.