Final answer:
An unstressed syllable followed by a stressed syllable is known as an iamb, which is a common meter in English poetry that creates a rhythmic pattern in the text.
Step-by-step explanation:
An unstressed syllable followed by a stressed syllable constitutes a iamb. The meter of poetry often relies on units called feet, which are sequences of stressed and unstressed syllables.
The iamb, specifically, is the most common foot in English and is used to create a rhythmic pulse within a line due to its rising rhythm - an example being the word 'forgot', where it naturally aligns to the iambic pattern (x /).