I'm so confused about dangling participles in sentences. For example,
In spite of taking medicine, my health is not improved..
Is this sentence a dangling participle? Why or why not? Explain it to me.
The dangling modifier clause, of which the dangling participle is the example most famously derided by teachers of English for a century, is the term we use to describe a situation in which part of a sentence lacks a specific subject, or refers unintentionally to the wrong subject. Frequently, such sentences include a modifier clause followed by a main clause, and it is in the main clause where we expect that subject to be provided. Your sentence is an excellent example of this construction:
In spite of taking medicine, my health is not improved.
The modifier which is accused of doing the dangling here is the bolded clause In spite of taking medicine, and a strict parsing of the sentence tells us that the subject of the modifier is my health in the main clause. Obviously, my health can't take any medicine at all. Your instructor wants you to write the sentence as, for instance:
In spite of taking medicine, I have not improved my health.
In spite of my taking medicine, my health has not improved.
Yet anyone who reads your original sentence can make perfect sense of it:
My health is not improved even though I've been taking medicine.
Why then would an instructor point out this clause as a ☞☞ ¡¡Dangling Participle!! ☜☜ and demand that it be banished from the sentence? After all, the function of language is to communicate. If a sentence clearly communicates the thought with which it is charged, has it not fulfilled its function? If the meaning is clear, what difference does it make? The answer, in the context of one particular sentence, may be:
No difference at all!
As Steven Pinker puts it in an interview with Science of Us:
If you look at the history of scholars who have examined the dangling modifier rule, you find that it was pretty much pulled out of thin air by one usage guide a century ago and copied into every one since, And you also find that lots of sentences read much better if you leave the modifier dangling.
However, there are still good reasons to learn what a dangling modifier clause is, and there are good reasons (especially for beginning students of English) to avoid using them.
English literature is resplendent with well-written and evocative dangling modifiers. Mr Shakespeare, whom we credit with inventing many of the words we use today, put these in the mouth of the Prince of Denmark:
Sleeping in mine orchard, a serpent stung me.
In the centuries since that was written, none among the play's audiences have interrupted the scene to ask how a sleeping serpent could have bitten Claudius's nephew. It also turns out that across those centuries, there never was a rule prohibiting the use of a dangling modifier. Generations of instructors have blindly passed the "rule" along after its initial appearance in a single usage guide over a century ago. Why did they do that, and why do they still do that? In some cases it's because they don't know that there is no such "rule." In other cases, it's because they aren't really interested in the language they are teaching, and having a list of prohibited things simplifies their job as instructors. They need only provide a list.
An instructor who claims that the rules of English grammar proscribe the use of a dangling modifier is wrong (although it will not be wise in most cases to dispute the issue with that instructor until after one's grade has been entered.)
Yet it turns out that there are very good reasons for a beginning student of English to recognize and eliminate the dangling modifier. One is to avoid writing things like the following:
He wore a straw hat on his head, which was obviously too small.
There are many compendia of humorous dangling modifers available to interested searchers. In most cases, a writer will not be pleased to see her writing so honored. Aside from the danger of unintentionally humorous interpretations, there is another good reason for beginning students to observe the advice to avoid the dangling modifier. The sport of tennis provides a good analogy here. No one doubts that Roger Federer and Andy Murray can play a game of tennis without a net between them. Two beginning players, though, absolutely require one. The same principle applies here: learn what the dangler is, understand the reason for the advice (not a rule!) against using it, and observe the advice when you begin to learn the language. Once you are fluent, you will be able to dangle modifiers to no ill effect; until then, play the game with a net.
Finally, it is wisest to side with Geoffrey Pullum and refer to the use of the dangler not as a violation of a "rule" but as a breach of courtesy. As a writer, it's simple courtesy to make the reader's task as easy as possible, and danglers often require the reader to pause, back up a few words, and puzzle out the meaning. His eloquence exceeds mine by an order of magnitude, and so this answer closes with a link to Mr Pullum's Language Log post entitled A dangler in The Economist.