This means that:
* Unrhymed: The lines do not rhyme with each other.
* Iambic Pentameter: Each line has ten syllables, with an alternating pattern of unstressed and stressed syllables (da-DUM da-DUM da-DUM da-DUM da-DUM).
The use of blank verse gives the play a formal, elevated tone, fitting for the subject matter of Thomas Becket's martyrdom. It also allows for flexibility in rhythm and pacing, and provides a natural flow for the dialogue.