Which type of poem is characterized by a specific structure and often expresses deep emotions?

A sonnet is a highly structured type of poem that typically consists of 14 lines and follows a specific rhyme scheme and meter, often iambic pentameter. This form allows poets to explore complex emotions and ideas within a confined space, leading to a powerful expression of feelings. The sonnet often delves into themes of love, nature, and philosophical concepts, making it a popular choice for poets to convey deep emotional experiences.

The other types of poems listed, while they may also express emotions, do not possess the same rigid structure and formal rules as a sonnet. For instance, a haiku is a three-line poem with a 5-7-5 syllable pattern that captures a moment in nature, but it does not delve as deeply into complex emotions. Lined poems and ballads can vary greatly in structure and content, leading to less consistency in their emotional expression compared to the sonnet format.