Final answer:
In "The Tyger," the four-line stanzas are called quatrains, a very common type of stanza in poetry.
Step-by-step explanation:
The four-line stanzas in the poem "The Tyger" by William Blake are called quatrains. A quatrain is one of the most common stanza forms in English poetry, which can have various rhyme schemes, such as AABB, ABBA, or ABCB. In the context of "The Tyger," each quatrain contributes to the overall rhythmic and thematic structure of the poem.