A dangling modifier is a phrase or clause which says something different from what is meant because words are left out. The meaning of the sentence, therefore, is left “dangling.”
Incorrect: While driving on Greenwood Avenue yesterday afternoon, a tree began to fall toward Wendy H’s car.
(It sounds like the tree was driving! This actually appeared in a newspaper article. An alert reader wrote, “Is the Department of Motor Vehicles branching out and issuing licenses to hardwoods? Have they taken leaf of their senses?”)
Adding a word or two makes the sentence clear.
Correct: While Wendy H was driving on Greenwood Avenue yesterday afternoon, a tree began to fall toward her car.
When a modifier “dangles” so that the sentence is meaningless (or means something other than your intent), restate it and add the words it needs in order to make sense.