Why Iambic Pentameter?

In this post I am going to try to answer a question that I frequently encounter: why iambic pentameter? What is so special about this particular meter, as compared to any other?

There are two aspects to look at here: the beat pattern, and the number of beats.

Let’s look first at the number of beats: five in a pentameter (“penta” is Greek for “five”, as in “pentagon”).

The five-beat iambic line is uniquely flexible and sinuous. Why? Because if the line is any longer, it tends to break down into component parts; and if it’s any shorter, it has a much more insistent rhythm.

So if we look at the longer lines first, the 6-beat hexameter (alternatively known as “Alexandrines”) has a tendency to break in the middle, producing what sounds like two trimeter (3-beat) lines. The 7-beat heptameter has a tendency to break down into component parts of 4 & 3 beats.

Shakespeare’s dramatic verse is peppered with the occasional hexameter, and he actively makes use of it’s tendency to break in the middle, allowing the second half of the line to build on, or answer, the first.

So, for instance, he sometimes used hexameters for shared lines: lines where one character completes the line started by another. A particularly wonderful example of this is the wooing scene between Richard of Gloucester and Lady Anne in Richard III (which I explore in parts 2 & 3 of this post: Iambic pentameter & the principles of metrical variation: part 3 – double trochees, hexameters, epic caesuras in shared lines, missing syllables, emphasis on a non-beat syllable & the false choriamb).

And here’s a line from Measure for Measure, in which the symmetrical balance provided by the hexameter line seems very appropriate:

To have what we would have, we speak not what we mean

So – what about shorter meters?

As I mentioned earlier, shorter meters have a much more insistent, monotonous rhythm, which is more suited to song than speech – and shorter meters are used in his songs and chants. To illustrate the monotony of the 4-beat tetrameter, let’s compare some lines of beats.

Read this out loud:


As I’m sure you can tell, the rhythm is unvarying and monotonous. We automatically tend to hear beats in pairs, so the effect is very similar to simply listening to a long string of beats: di-dum-di-dum-di-dum-di-dum-di-dum-di-dum-di-dum-di-dum

Now read this out loud:


Can you hear the difference? There’s a natural pause at the end of each line: the rhythm is no longer unvaried and monotonous. You now have a meter that’s more subtle and interesting to play with, and far more suited to conveying human speech.

The key here is that the pentameter is asymmetrical, because it has an odd number of beats. The 7-beat heptameter is also asymmetrical, but is too long and unwieldy to maintain cohesion, and breaks down into component parts. And the 3-beat trimeter is far too short and abrupt to accommodate all the nuances of human speech. The 5-beat pentameter is, as Goldilocks would say, just right.

I explore variations in line length further in this post: What are some examples of iambic meter?

Now let’s look at the beat pattern.

“Iambic” refers to the basic patterning: the beat landing on every other syllable (when an iambic line is broken up into individual “feet” for the sake of analysis, each “di-dum” is called an “iamb”).

So, what are the alternatives?

The first alternative is to open on the beat: “dum-di-dum-di-dum…”. This meter is called either “trochaic” or “headless” (I prefer “headless”). The impact of opening on the beat is weakened in lines of 5 beats, so nearly all headless poems are written in lines of 4 beats or less.

For a poet, headless meters are a straitjacket. The first beat has to be strong. And without the introductory non-beat syllable to glide you in and establish an iambic beat patterning from the off, you are obliged to commit to an unvaried beat pattern to assert the rhythm: you can no longer shift any of the beats (I explain displaced beats here: Iambic pentameter & the principles of metrical variation: part 2 – radical variations)

In short, headless meters lack the flexibility or fluidity of iambic meters. However, the abrupt, emphatic quality of headless meters can certainly be put to highly effective use:

Round about the cauldron go
In the poisoned entrails throw
Toad that under cold _ stone
Days and nights has thirty-one
Sweltered venom sleeping got
Boil thou first i’ th’ charmed pot.
Double, double, toil and trouble
Fire burn and cauldron bubble.

It can also have a simple, nursery rhyme quality:

Where the bee sucks, there suck I,
In a cowslips bell I lie;
There I couch when owls do cry.
On the bat’s back I do fly
After summer merrily,

Shakespeare does use the occasional headless line in his pentameter verse for the sake of emphasis – as in this exclamation from Mercutio (“Romeo” is here pronounced as two syllables: Rome-yo):

Where the devil should this Romeo be

(I explore headless meters thoroughly in this post: What-are-the-differences-betweeniambic-and-trochaic-meters?. In the second half of the post, I also explore how rising and falling rhythms are created by the words and phrases within the line).

The second alternative is to have two syllables between every beat: “di-di-dum-di-di-dum-di-di-dum…”. This is called “anapestic” meter. Again, you can also open on the beat: “dum-di-di-dum-di-di-dum…”. This is known as either “dactylic” or “headless anapestic” meter. Again the rhythm is very emphatic, with the run up of two light syllables hitting each beat. It is no coincidence that two of the best known examples of this swift, galloping rhythm involve depictions of cavalry charges: the-destruction-of-sennacherib the-chargeofthelightbrigade

The last two lines of Ariel’s Song, which I quoted from earlier, follow this rhythm, providing a delightful, lively, skipping quality:

Merrily, merrily shall I live now,
Under the blossom that hangs on the bough

Iambs and anapests can also be intermixed. It is very common, for instance that some of the lines in an anapestic poem open with an iamb (just one light syllable before the beat) as is the case in Byron’s poem: “The lances unlifted the trumpet unblown”. When iambs and anapests are freely intermixed, it produces a loose feel to the meter (here’s a particularly fine example: Mowing by Robert Frost. The anapests echo the “whispering” scythe. And I’ve just noticed that last sentence is itself anapestic: “The anapests echo the whispering scythe”!).

Though Shakespeare frequently glided together words and syllables, especially in his later plays, he very rarely employed unambiguous anapests – which means that when he did, it stood out! A charming example can be found in the very last line of The Comedy of Errors:

We came into the world like brother and brother
And now let’s go hand in hand, not one before the other.

There is a gliding together of words towards the end of the penultimate line (brother’nd brother), and the final line opens with an anapest: “And now let’s go hand in hand…”. The light, tripping effect this produces is really joyous and uplifting!

And that seems the perfect note to end on!


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