Here's why:
* Formal Diction: Rossetti uses elevated language, avoiding slang and contractions.
* Complex Sentence Structure: The poem features complex sentence structures with dependent clauses and sophisticated grammar.
* Figurative Language: The poem employs metaphors, similes, and personification, which are common in formal poetry.
* Rhyme and Meter: The poem adheres to a strict ABAB rhyme scheme and a regular iambic pentameter, contributing to its formal tone.
While "In a Birthday" does touch upon themes of love and longing, it maintains a controlled and dignified tone, consistent with the expectations of formal writing in the Victorian era.