Final answer:
Sir Gawain and the Green Knight uses Middle English and alliterative verse, differing from iambic pentameter and heroic couplets found in other English poetry.
Step-by-step explanation:
The poem Sir Gawain and the Green Knight is characterized by its use of Middle English and a meter that is often referred to as the alliterative verse. This type of meter is distinguished from more commonly known metrical patterns such as iambic pentameter, which is often associated with Shakespearean works, or the heroic couplets seen in the poetry of Alexander Pope. Instead of a strict adherence to syllabic count and standard metrical feet like iambs or trochees, alliterative verse relies on the repetition of consonant sounds at the beginning of words within a line of poetry. Examples of this alliterative pattern can be found in the poetry of the Anglo-Saxon era, such as Beowulf, as well as later works such as Sir Gawain and the Green Knight.