The word, MODIFIER, is used in grammar to mean generally any part of speech that describes or adds detail. Another way to think of it is as a word or a set of words that informs us about how a thing or an action can be perceived. For example, a dog perceived to be scared and agitated is "a nervous dog": "nervous" is a modifier. A dog perceived to be waving its hindquarters with enthusiasm "happily wags its tail": "happily" is a modifier. The word or words that a modifier describes are referred to as the modifier's SUBJECT.
A modifier can be just a single word, a phrase, or an entire dependent clause. Though one or two other parts of speech are similar to modifiers, virtually all modifiers are either adjectival or adverbial, and break down into the categories listed in the menu at left. These include the following:
Appositives and appositive phrases are technically not modifiers, but they function similarly to rename another noun with added specificity or detail. An appositive is a noun or noun phrases placed side-by-side with another noun or pronoun. For example, "Tonka, the family's beloved bull terrier"; the phrase, "the family's beloved bull terrier," restates "Tonka" with greater and clearer detail. Appositives are given their due elsewhere on this website, under "Noun Phrases and Clauses."
Though modifiers are either adjectival or adverbial, they aren't always expressed that way in colloquial English. Take, for instance, the frequently heard phrase, "Eat healthy." If "eat" is the subject of the modifier "healthy," then an adverb, not an adjective, is needed: "healthily" or "healthfully."
Furthermore, modifiers work best only when readers understand first what their subjects are. When the subjects of modifiers are not clearly understood, or cannot be found in the sentence at all, mistakes occur. For example, had my last sentence begun, "Modifiers only work best...," the word "only" would have been taken to mean "Modifiers only" instead of "only work." These types of modifier errors can sometimes lead to humorous miscommunication—and "sometimes can lead" is different from saying they can lead to "sometimes hilarious" miscommunication.
Such confusion among modifiers is also addressed in this section.