Modifiers are words or phrases that describe something else, and can sometimes be confusing or ambiguous when arranged in certain ways, as with misplaced, dangling, or squinting modifiers.

Examples:

He wore a helmet on his head that was too large.

Correct sentence: He wore a helmet that was too large on his head.

A misplaced modifier is a word, phrase, or clause that is improperly separated from the word it modifies / describes.

Examples:

The patient was referred to the physician with a headache.

Correct sentence: The patient with a headache was referred to the physician.

A dangling modifier is a word or phrase that modifies a word not clearly stated in the sentence.

Examples:

Riding on the sports bike, the world whizzed by rapidly.

Correct sentence: As Peter was riding on the sports bike, the world whizzed by rapidly.

A squinting modifier is a word that describes something but that is out of place.

Examples:

Saving a life often made Max feel proud.

Correct sentence: Saving a life made Max feel proud often.