Playing to our own rules: Poetic constraint

Arma virumque cano – ‘I sing of arms and the man’. With these resonant words Virgil opens his great epic the Aeneid, composed over two thousand years ago. The poem, which is nearly ten thousand lines long, is written almost entirely in dactylic hexameter – an astonishing feat of constrained writing, especially when we consider that Virgil lacked the convenience of our modern-day word processing and editing tools.

Constraint – be it of metre, rhyme, form, or shape – has been a feature of poetry throughout the ages. The pattern poems of  Simias of Rhodes for example, which were composed around 300 BC, are constrained by shape. A Shakespearean sonnet is constrained by its metre (iambic pentameter), rhyme scheme (ABAB CDCD EFEF GG) and form (14 lines, typically with a volta, or turn, in the final two lines). A sestina is constrained by the permutation through the stanzas of six end-words in a particular sequence.

Generally, however, when we think of constrained writing we have more experimental forms in mind. Contemporary constrained poetry owes much to the Oulipo movement, which was founded in 1960 by Raymond Queneau and François Le Lionnais. Queneau described the Oulipian approach as analogous to that of ‘rats who construct the labyrinth from which they plan to escape’. Lipograms, anagrams, palindromes, univocalism and mathematical patterning have all been explored by Oulipian members. 

The application of rigorous constraint is often characterised by a sense of adventure, of playfulness – given a set of rules, what patterns, what behaviours, can we tease out of these words? How far can we push language within our chosen boundaries while at the same time maintaining integrity of meaningfulness and grammatical structure? Is there scope within the application of constraint to elicit an emotional response from the reader, or perhaps to generate an interactive response at a more technical level?

Constraint within a poem frequently operates concurrently on two levels, which I shall call structural constraint and unit constraint. Our structural constraint, for example, may be a palindrome – a poem that reads the same backwards as well as forwards. Within that structure our unit of constraint may be palindrome by line, or by word, or by letter, or even by letter clusters grouped according to numerical sequences, as in Anthony Etherin’s aelindromes

There may also be additional structural constraints. A palindrome may be a sonnet, or a haiku, or it may conform to a rhyme scheme or metrical pattern.

To explore the idea of structural and unit constraints in more detail, let’s consider Fib poems – poems based on the Fibonacci sequence

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …

I am drawn to this structure, partly for its mathematical resonance and partly for its flexibility. Playing with the layout and arrangement of lines can give rise to interesting visual effects. The sequence is also associated with biological growth and patterning, themes that I like to explore in my writing.

The unit of constraint in my poem below is the syllable:

Post lockdown

from our aloneness
like fragile shoots that, warmed by spring,
open to the light. Let us be gentle with our smiles, 
be tender with our touch.  For who knows the sadness that has petrified inside our hearts?

By way of contrast, the unit of constraint in my poem ‘Pathways’ is the letter:

by life’s patterns: a whorl
in a pinecone, branches on oak or elm trees, 
the petal count of a daisy, the helix at the heart of a chrysanthemum,
the shell of a nautilus swimming in the ocean. A sequence hides in the shape of probabilities, and in my own DNA.

The last line of this poem has 89 letters. There is an additional unit of constraint – the letters of each word add up to a Fibonacci number (‘chrysanthemum’, for example, has 13 letters).

‘Returning’ by Anthony Etherin has a double structural constraint and a double unit constraint. The number of syllables per line is defined by the Fibonacci sequence, while the poem is also a palindrome by word. 


to arches
returning form and
close, now, far shape…. Then, shape far, now
close and form returning arches, to spiral the weave.

Note how elegantly this poem signifies, in both structure and content, the Fibonacci spiral, which is illustrated below (source: Wikipedia):

The progression in line length that is inherent to a Fib poem can be exploited for visual effect. When writing my poem ‘Crochet’, for example, I had in mind a triangular shawl. In order to convey shape and pattern, I used spacing and mirror symmetry of syllable count within each line:

In the final line there is a clinamen – a deviation from the strict constraints I set myself – in keeping with the sentiment expressed.


this     fine
spun     wool     hand
dyed     in     shades     of     gold
sift     its     texture     balance     the     hook
patiently     loop     stitches and spaces     turn     sequencing
intricately patterned rows     presences and absences     life's imperfect symmetry

Further examples of visual shaping in a Fib poem include A.E. Weisberger’s ‘Mary-Pat’ (which uses a character/space constraint), Tyson West’s ‘Equis Homo’ (syllable constraint with paired decreasing lines) and my poem ‘And for the rest of time’ (syllable constraint, with fragmented lines in the second half of the poem).

‘A Falling Inward’ by Greg Hill, where the unit of constraint is the word, has an aesthetically pleasing diamond shape. As Hill explains, the poem has two structural constraints, as well as an additional unit constraint (every word is unique): 

‘For the first six lines, the number of words in each line corresponds to the Fibonacci sequence (1, 1, 2, 3, 5, 8), after which the order reverses (5, 3, 2, 1, 1). In addition, for the entirety of the poem, the first letter of each word (e.g., c, a, d, a, e, i, …) corresponds to the digits of pi: 3, 1, 4, 1, 5, 9, … (where a=1, b=2, c=3, and so forth). As a further constraint, no words in the poem are repeated. Like falling in love, the theme of the poem, the Fibonacci sequence builds on its past, and, like the digits of pi, progresses forever, without repeating.’

Fibonacci and π dance together in this joyous celebration of love, poetry and mathematics. We sense that the poet had as much enjoyment writing it as we have in reading it.

A Falling Inward

dance again!
excellence inside, born 
from experience. celebrate everyone. here
in gratitude, inamorata: collapsing bodies, close hearts divining—
finding best friends daring, carefree, 
companions hopeful, circling, 
beginning gambols 


With thanks to Anthony Etherin and Greg Hill for generously granting permission to quote their work. All the poems given here were originally published in the Fib Review, with the exception of ‘Pathways’ which first appeared in Independent Variable.

Further Reading

Jan Baetens and Jean-Jacques Poucel (2009) Introduction: The Challenge of Constraint. Poetics Today 1 December 2009; 30 (4): 611–634. Available at

Daniel Cartwright (2019) The Oulipo and Modernism: Literature, Craft and Mathematical Form. PhD thesis University of Westminster School of Humanities. Available at

Marian Christie (2021) From Fibs to Fractals: Exploring mathematical forms in poetry. Beir Bua Press.

Rebecca Hazelton (2017) The Choice of Constraint. Available at

Philip Terry (ed) (2019) The Penguin Book of Oulipo. Penguin Random House UK

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  1. Pingback: What Will People Say? – Ren Powell | Poet & Teaching Artist

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