Which one of the following works is NOT a ballet composed by Tchaikovsky?

The work that is not a ballet composed by Tchaikovsky is "Romeo and Juliet." While Tchaikovsky did create a famous orchestral work titled "Romeo and Juliet," it is a concert overture and not a ballet. This piece, based on Shakespeare's play, is a symphonic poem that captures the emotional depth and drama of the story through orchestral music rather than through dance.

In contrast, "The Nutcracker," "Swan Lake," and "Sleeping Beauty" are all well-known ballets, specifically choreographed to Tchaikovsky's music. These ballets incorporate dance performances and are structured around choreographed movements that tell stories through the combination of music and ballet. Therefore, "Romeo and Juliet" stands out as the piece that does not fit within the category of ballets.