Shakespeare's plays are written in a mixture of poetry and prose. In general, noble characters speak poetry, and common or comic characters speak prose. Shakespeare's audience would hear this as a shift from the heightened language of court to the "everyday" language of the street. In Othello, the prose passages are most often conversations that Iago has, "behind the scenes" (often, near the end of a scene), with Roderigo or with Cassio.
When the characters speak poetry, they usually speak in unrhymed lines of iambic pentameter (also known as "blank verse"). The term "iambic pentameter" is a way of describing the rhythm and length of the line. We divide a line of poetry into patterns of stressed and unstressed syllables (called metrical feet). "Iambic" refers to one of these patterns (unstressed-stressed, or bum-BUM), and "pentameter" refers to the number of these feet in the line (penta-, five).
The names of the common patterns or metrical feet are listed at the bottom of this page. But more important than learning the names, is learning to hear (and to feel, with your voice) the basic rhythm underlying Shakespeare's lines: bum BUM, bum BUM, bum BUM, bum BUM, bum BUM. It's no accident that iambic pentameter is the most common rhythm in English poetry: it IS the NATural RHYthm OF our LANGuage!
Obviously, if every line were written precisely and unchangingly in this pattern — bum BUM, bum BUM, bum BUM, bum BUM, bum BUM— the result would be sing-songy and childish. The power of poetry lies in the tension between this underlying rhythm and the variations that arise when we follow the sense of the words rather than the arbitrary pattern. And although Shakespeare varies the pattern frequently, there are some basic "rules" that can actually help you with the pronunciation and meaning of words: There are seldom (if ever) more than two unstressed syllables in a row. Conversely, there are seldom more than two stressed syllables in a row.
Again, the point here is not to break every line into its metrical feet (a form of analysis called "scansion"), but to hear and feel the rhythm and let it help you give voice to what a character is saying and feeling. Below are the closing lines of Act 1, Scene 2, with the unstressed syllables in black, stressed syllables in red, and the metrical feet divided by a slash (/).
For one of the lines, I have included both the natural stresses (the way we might actually say the line) and the underlying (but arbitrary, and at times forced) pattern of iambic pentameter. The first line and a half are spoken by the Officer; the rest by Brabantio. Note how the Officer and Brabantio "share" that second line (which explains the indentation you will find here and elsewhere where two characters "share" the five feet of a single line of iambic pentameter. In fact, here the Officer and Brabantio split the line right down the middle, right in the middle of the third foot!
Iambic pentameter = five metrical feet in the pattern “bum BUM.”
iamb = bum BUM (iambic)
trochi = BUM bum (trochaic)
anapest = bum bum BUM (anapestic)
dactyl = BUM bum bum (dactylic)
spondee = BUM BUM (rarely used)
With a couple of stretches these names follow the pattern they describe (a good pnemonic device):
i AM! (it’s really pronounced I am, but imagine it as an exclamation)
DACtylic (it’s really pronounced dacTYLic)