In a line of verse that normally employs iambic meter, trochaic substitution describes the replacement of an iamb by a trochee.
The following line from John Keats's To Autumn is straightforward iambic pentameter:[2] Using '°' for a weak syllable, '/' for a strong syllable, and '|' for divisions between feet it can be represented as: The opening of a sonnet by John Donne demonstrates trochaic substitution of the first foot ("Batter"): Donne uses an inversion (DUM da instead of da DUM) in the first foot of the first line to stress the key verb, "batter", and then sets up a clear iambic pattern with the rest of the line Shakespeare's Hamlet includes a well-known example: In the first line the word that is stressed rather than is, which would be an unnatural accent.
The first syllable of Whether is also stressed, making a trochaic beginning to the line.
John Milton used this technique extensively, prompting the critic F. R. Leavis to insultingly call this technique the Miltonic Thump.
[3] Sometimes the opposite substitution, of an iamb in place of a trochee, is found.