Final answer:
In a Shakespearean sonnet, the usual meter used is iambic pentameter, which consists of five pairs of alternating unstressed and stressed syllables per line.
Step-by-step explanation:
In a Shakespearean sonnet, the usual meter used is iambic pentameter. This means that each line consists of five sets of iambs; an iamb is a metrical foot with one unstressed syllable followed by a stressed syllable, resembling a heartbeat with a 'da-dum' sound. Consider the famous first line from Shakespeare's Sonnet 18, where the stressed syllables are highlighted to show the iambic pentameter in action:
'Shall I compare thee to a summer's day?'
Here, each 'da-DUM' represents one iamb, and since there are five such pairs in a line, it is called pentameter. It is the meter of choice not only for sonnets but for much of Shakespeare's dramatic verse as well, providing a rhythmic structure while allowing for variations that avoid monotony and enhance the expressive quality of the text.