Iambic Pentameter

The Iambic Pentameter is a dramatic device used to determine dramatic verse in classical theatre. It is the particular rhythm that the words establish in that line. That rhythm is measured in small groups of syllables; these small groups of syllables are called "feet". The word "iambic" describes the type of foot that is used (in English, an unstressed syllable followed by a stressed syllable). The word "pentameter" indicates that a line has five of these "feet."

The da-DUM of a human heartbeat is the most common example of this rhythm.

A standard line of iambic pentameter is five iambic feet in a row:

da DUM da DUM da DUM da DUM da DUM

Shakespeare's Hamlet is the best example of a line that defies the rule as it holds a feminine ending. 

 ×  / ×   /   ×  /      /  ×    ×   / (×)
To be or not to be, | that is the question
The extra unstressed syllable marks the feminine ending, and here is an example of a caesura, a   pause held in the middle of a line that could mark a change of thought or act as a middle                line-ending.