A dangling modifier (also known as a dangling participle, illogical participle or hanging participle) is a type of ambiguous grammatical construct whereby a grammatical modifier could be misinterpreted as being associated with a word other than the one intended. A dangling modifier has no subject and is usually a participle. A writer may use a dangling modifier intending to modify a subject while word order may imply that the modifier describes an object, or vice versa.

An example of a dangling modifier appears in the sentence "Turning the corner, a handsome school building appeared". The modifying clause Turning the corner describes the behavior of the narrator, but the narrator is only implicit in the sentence. The sentence could be misread, with the turning action attaching either to the handsome school building or to nothing at all. As another example, in the sentence "At the age of eight, my family finally bought a dog", the modifier At the age of eight is dangling. It is intended to specify the narrator's age when the family bought the dog, but the narrator is again only implicitly a part of the sentence. It could be read as the family was eight years old when it bought the dog.

As an adjunct, a modifier clause is normally at the beginning or the end of a sentence and usually attached to the subject of the main clause. However, when the subject is missing or the clause attaches itself to another object in a sentence, the clause is seemingly "hanging" on nothing or on an inappropriate noun. It thus "dangles", as in these sentences:

Ambiguous: Walking down Main Street (clause), the trees were beautiful (object). (Subject is unclear / implicit)

Unambiguous: Walking down Main Street (clause), I (subject) admired the beautiful trees (object).

Ambiguous: Reaching the station, the sun came out. (Subject is unclear - who reached the station?)

Unambiguous: As Priscilla reached the station, the sun came out.

In the first sentence, the adjunct clause may at first appear to modify "the trees", the subject of the sentence. However, it actually modifies the speaker of the sentence, who is not explicitly mentioned. In the second sentence, the adjunct may at first appear to modify "the sun", the subject of the sentence. Presumably, there is another, human subject who did reach the station as the sun was coming out, but this subject is not mentioned in the text. In both cases, whether the intended meaning is obscured or not may depend on context - if the previous sentences clearly established a subject, then it may be obvious who was walking down Main Street or reaching the station. But if left alone, they may be unclear if the reader takes the subject as an unknown observer; or misleading if a reader somehow believed the trees were walking down the street or the sun traveled to the station.