Final answer:
The poem "When I Have Fears" is a sonnet, specifically a Shakespearean sonnet, characterized by its 14 lines and ABAB CDCD EFEF GG rhyme scheme.
Step-by-step explanation:
The literary form that "When I Have Fears" imitates is a sonnet. Specifically, it follows the structure of a Shakespearean sonnet, which is noted for its three quatrains (groups of four lines) and a concluding couplet (two lines), making it a 14-line poem in total. The rhyme scheme for a Shakespearean sonnet is ABAB CDCD EFEF GG, which is different from other sonnet forms like the Italian or Petrarchan sonnet. Sonnets typically discuss themes of love, beauty, politics, mortality, and nature, containing a volta or turn in thought. "When I Have Fears" employs this structure to explore the poet's anxieties about death and the loss of opportunities to experience love and write down all his thoughts.