Dactylic hexameter (also known as "heroic hexameter") is a form of meter in poetry or a rhythmic scheme. It is traditionally associated with the quantitative meter of classical epic poetry in both Greek and Latin, and was consequently considered to be the Grand Style of classical poetry. The premier examples of its use are Homer's Iliad and Odyssey and Virgil's Aeneid.
The meter consists of lines made from six ("hexa") feet. In strict dactylic hexameter, each of these feet would be a dactyl, but classical meter allows for the substitution of a spondee in place of a dactyl in most positions. Specifically, the first four feet can either be dactyls or spondees more or less freely. The fifth foot is frequently a dactyl (around 95% of the time in Homer). The sixth foot is always a spondee, though it may be anceps. Thus the dactylic line most normally looks as follows:
- — U | — U | — U | — U | — u u | — X
(note that — is a long syllable, u a short syllable and U either one long or two shorts and X anceps syllable)
Hexameters also have a primary caesura — a break in sense, much like the function of a comma in prose — at one of several normal positions: After the first syllable in the third foot (the "masculine" caesura); after the second syllable in the third foot if the third foot is a dactyl (the "feminine" caesura); after the first syllable of the fourth foot; or after the first syllable of the second foot (the latter two often occur together in a line, breaking it into three separate units). The first possible caesura that one encounters in a line is considered the main caesura.
In addition, hexameters have two bridges, places where there very rarely is a break in a word-unit. The first, known as Meyer's Bridge, is in the second foot: if the second foot is a dactyl, the two short syllables must be part of the same word-unit. The second, known as Hermann's Bridge, is the same rule in the fourth foot: if the fourth foot is a dactyl, the two short syllables must also be part of the same word-unit.
Hexameters are frequently enjambed, which helps to create the long, flowing narrative of epic. They are generally considered the most grandiose and formal meter.
An English language example of the dactylic hexameter, in quantitative meter:
- Down in a | deep dark | hole sat an | old pig | munching a | bean stalk
As the absurd meaning of this example demonstrates, quantitative meter is extremely difficult to construct in English. Here is an example in normal stress meter (the first line of Longfellow's "Evangeline"):
- This is the | forest pri | meval. The | murmuring | pines and the | hemlocks
The "foot" is often compared to a musical measure and the long and short syllables to half notes (minims) and quarter notes (crotchets), respectively.
Homer’s meter 
The hexameter was first used by early Greek poets of the oral tradition, and the most complete extant examples of their works are the Iliad and the Odyssey, which influenced the authors of all later classical epics that survive today. Early epic poetry was also accompanied by music, and pitch changes associated with the accented Greek must have highlighted the melody, though the exact mechanism is still a topic of discussion.
The Homeric poems arrange words in the line so that there is an interplay between the metrical ictus—the first long syllable of each foot—and the natural, spoken accent of words. If these two features of the language coincide too frequently, they overemphasize each other and the hexameter becomes sing-songy. Nevertheless, some reinforcement is desirable so that the poem has a natural rhythm. Balancing these two considerations is what eventually leads to rules regarding the correct placement of the caesura and breaks between words; in general, word breaks occur in the middle of metrical feet, while accent and ictus coincide only near the end of the line.
The first line of Homer’s Iliad—“Sing, goddess, the anger of Peleus’ son Achilles”—provides an example:
- μῆνιν ἄειδε, θεά, Πηληϊάδεω Ἀχιλῆος
Dividing the line into metrical units:
- μῆνιν ἄ | ειδε, θε | ά, Πη | ληϊά | δεω Ἀχι | λῆος – dactyl, dactyl, spondee, dactyl, dactyl, trochee.
Note how the word endings do not coincide with the end of a metrical foot; for the early part of the line this forces the natural accent of each word to lie in the middle of a foot, playing against the natural rhythm of the ictus.
This line also includes a masculine caesura after θεά, a natural break that separates the line into two logical parts. Unlike later writers, Homeric lines more commonly employ the feminine caesura; an example occurs in Iliad I.5 “...and every bird; thus the plan of Zeus came to fulfillment”:
- οἰωνοῖσί τε πᾶσι, Διὸς δ’ ἐτελείετο βουλή,
- οἰω | νοῖσί τε | πᾶσι, Δι | ὸς δ’ ἐτε | λείετο | βουλή,
Homer’s hexameters contain a far higher proportion of dactyls than later hexameter poetry. They are also characterised by a laxer following of verse principles that the authors of later epics almost invariably adhered to. For example, Homer allows spondaic fifth feet (albeit not often), whereas many later authors virtually never did. There are also exceptions to Meyer’s Bridge and Hermann’s Bridge in Homer (albeit rare), but such violations are exceedingly rare in a later author like Callimachus.
Homer also altered the forms of words to allow them to fit the hexameter, typically by using a dialectal form: ptolis is an epic form used instead of the Attic polis wherever it is necessary for the meter. On occasion, the names of characters themselves actually seem to have been altered: the spelling of the name of Homer’s character Polydamas, Pouludamas, appears to be an alternative rendering of the metrically unviable Poludamas (“subduer of many”).
Finally, even after accepting the various alterations admitted by Homer, some lines remain impossible to scan, e.g. Iliad I.108 “not a good word spoken nor brought to pass”:
- ἐσθλὸν δ’ οὐτέ τί πω εἶπας ἔπος οὔτ’ ἐτέλεσσας
The first three feet of this line scan spondee-dactyl-spondee, but the fourth foot of -πας ἔπος has three consecutive short syllables. These metrical inconsistencies (along with a knowledge of comparative linguistics) have led scholars to infer the presence of a lost digamma in the original Ionic text of the poem. In this example, the word ἔπος was originally ϝέπος in Ionian; the presence of this glide consonant lengthens the last syllable of the preceding εἶπας and corrects the apparent defect in the meter. This example demonstrates the oral tradition of the Homeric epics that flourished long before they were written down sometime in the 7th century BC.
In spite of the occasional exceptions in early epic, most of the later rules of hexameter composition have their origins in the methods and practices of Homer.
Latin hexameter 
The hexameter came into Latin as an adaptation from Greek long after the practice of singing the epics had faded. Consequentially, the properties of the meter were learned as specific "rules" rather than as a natural result of musical expression. Also, because the Latin language generally has a higher percentage of long syllables than Greek, it is by nature more spondaic than Greek. These factors caused the Latin hexameter to take on distinct Latin characteristics.
The earliest example of the use of hexameter in Latin poetry is that of the Annales of Ennius, which established the dactylic hexameter as the standard for later Latin epic. Later Republican writers, such as Lucretius, Catullus and even Cicero, wrote their own compositions in the meter and it was at this time that many of the principles of Latin hexameter were firmly established, ones that would govern later writers such as Virgil, Ovid, Lucan, and Juvenal. Virgil's opening line for the Aeneid is a classic example of Latin hexameter:
- Arma virumque cano, Troiae qui primus ab oris (dactyl, dactyl, spondee, spondee, dactyl, spondee)
As in Greek, lines were arranged such that the metrically long syllables—those occurring at the beginning of a foot—avoided the natural stress of a word. In the first few feet of the meter, meter and stress were expected to clash, while in the final few feet they were expected to resolve and coincide—an effect that gives each line a natural "dum-ditty-dum-dum" ("shave and a haircut") rhythm to close. Such an arrangement is a balance between an exaggerated emphasis on the metre—which would cause the verse to be sing-songy—and the need to provide some repeated rhythmic guide for skilled recitation.
In the following example of Ennius's early Latin hexameter composition, metrical weight ("ictus") falls on the first and last syllables of certabant; the ictus is therefore opposed to the natural stress on the second syllable when the word is pronounced. Similarly, the second syllable of the words urbem and Romam carry the metrical ictus even though the first is naturally stressed in typical pronunciation. In the closing feet of the line, the natural stress that falls on the third syllable of Remoramne and the second syllable of vocarent coincide with the metrical ictus and produce the characteristic "shave and a haircut" ending:
- certabant urbem Romam Remoramne vocarent.
- (Annales 1.86)
Like their Greek predecessors, classical Latin poets avoided a large number of word breaks at the ends of foot divisions except between the fourth and fifth, where it was encouraged. In order to preserve the rhythmic close, Latin poets avoided the placement of a single syllable or four-syllable word at the end of a line. The caesura is also handled far more strictly, with Homer's feminine caesura becoming exceedingly rare, and the second-foot caesura always paired with one in the fourth.
One example of the evolution of the Latin verse form can be seen in a comparative analysis of the use of spondees in Ennius' time vs. the Augustan age. The repeated use of the heavily spondaic line came to be frowned upon, as well as the use of a high proportion of spondees in both of the first two feet. The following lines of Ennius would not have been felt admissible by later authors since they both contain repeated spondees at the beginning of consecutive lines:
- his verbis: "o gnata, tibi sunt ante ferendae
- Aerumnae, post ex fluvio fortuna resistet."
- (Annales 1.42f)
Virgil and the Augustan poets 
By the age of Augustus, poets like Virgil closely followed the rules of the meter and approached it in a highly rhetorical way, looking for effects that can be exploited in skilled recitation. For example, the following line from the Aeneid (VIII.596) describes the movement of rushing horses and how "a hoof shakes the crumbling field with a galloping sound":
- quadrupedante putrem sonitu quatit ungula campum
This line is made up of five dactyls and a closing spondee, an unusual rhythmic arrangement that imitates the described action. A similar effect is found in VIII.452, where Virgil describes how the blacksmith sons of Vulcan "take up their arms with great strength one to another" in forging Aeneas' shield:
- illi inter sese multa ui bracchia tollunt
The line consists of all spondees except for the usual dactyl in the fifth foot, and is meant to mimic the pounding sound of the work. A third example that mixes the two effects comes from I.42, where Juno pouts that Athena was allowed to use Jove's thunderbolts to destroy Ajax ("she hurled Jove's quick fire from the clouds"):
- Ipsa Jovis rapidum jaculata e nubibus ignem
This line is nearly all dactyls except for the spondee at -lata e. This change in rhythm paired with the harsh elision is intended to emphasize the crash of Athena's thunderbolt.
Virgil will occasionally deviate from the strict rules of the meter to produce a special effect. One example from I.105 describing a ship at sea during a storm has Virgil violating metrical standards to place a single-syllable word at the end of the line:
- ...et undis
- dat latus; insequitur cumulo praeruptus aquae mons.
The boat "gives its side to the waves; there comes next in a heap a steep mountain of water." By placing the monosyllable mons at the end of the line, Virgil interrupts the usual "shave and a haircut" pattern to produce a jarring rhythm, an effect that echoes the crash of a large wave against the side of a ship.
- Non quivis videt inmodulata poemata iudex,
The line, which lacks a proper caesura, is translated "Not every critic sees an inharmonious verse."
Silver Age and later heroic verse 
The verse innovations of the Augustan writers were carefully imitated by their successors in the Silver Age of Latin Literature. The verse form itself then was little changed, as the quality of a poet's hexameter was judged against the standard set by Virgil and the other Augustan poets, a respect for literary precedent encompassed by the Latin word aemulatio. Deviations were generally regarded as idiosyncrasies or hallmarks of personal style, and were not imitated by later poets. Juvenal, for example, was fond of occasionally creating verses that placed a sense break between the fourth and fifth foot (instead of in the usual caesura positions), but this technique—-known as the bucolic diaeresis-—did not catch on with other poets.
In the late empire, writers experimented again by adding unusual restrictions to the standard hexameter. The rhopalic verse of Ausonius is a good example; besides following the standard hexameter pattern, each word in the line is one syllable longer than the previous, e.g.:
- Spes, deus, aeternae stationis conciliator,
- si castis precibus veniales invigilamus,
- his, pater, oratis placabilis adstipulare.
Also notable is the tendency among late grammarians to thoroughly dissect the hexameters of Virgil and earlier poets. A treatise on poetry by Diomedes Grammaticus is a good example, as this work (among other things) categorizes dactylic hexameter verses in ways that were later interpreted under the golden line rubric. Independently, these two trends show the form becoming highly artificial—more like a puzzle to solve than a medium for personal poetic expression.
By the Middle Ages, some writers adopted more relaxed versions of the meter. Bernard of Cluny, for example, employs it in his De Contemptu Mundi, but ignores classical conventions in favor of accentual effects and predictable rhyme both within and between verses, e.g.:
- Hora novissima, tempora pessima sunt — vigilemus.
Ecce minaciter imminet arbiter ille supremus.
Imminet imminet ut mala terminet, æqua coronet,
Recta remuneret, anxia liberet, æthera donet.
- (I.1-4: These are the last days, the worst of times: let us keep watch. Behold the menacing arrival of the supreme Judge. He is coming, he is coming to end evil, crown the just, reward the right, set the worried free, and give the skies.)
Not all Medieval writers are so at odds with the Virgilian standard, and with the rediscovery of classical literature, later Medieval and Renaissance writers are far more orthodox, but by then the form had become an academic exercise. Petrarch, for example, devoted much time to his Africa, a dactylic hexameter epic on Scipio Africanus, but this work was unappreciated in his time and remains little read today. In contrast, Dante decided to write his epic, the Divine Comedy in Italian—a choice that defied the traditional epic choice of Latin dactylic hexameters—and produced a masterpiece beloved both then and now.
With the New Latin period, the language itself came to be regarded as a medium only for "serious" and learned expression, a view that left little room for Latin poetry. The emergence of Recent Latin in the 20th century restored classical orthodoxy among Latinists and sparked a general (if still academic) interest in the beauty of Latin poetry. Today, the modern Latin poets who use the dactylic hexameter are generally as faithful to Virgil as Rome's Silver Age poets.
- Cf. Alan Shaw's essay Some Questions on Greek Poetry and Music.
- Introduction to the dactylic hexameter for Latin verse.
- Reading dactylic hexameter, specifically Homer.
- Recitation of Homer, by Stanley Lombardo.
- Oral reading of Virgil's Aeneid, by Robert Sonkowsky, University of Minnesota.
- Greek hexameter analysis online tool, University of Vilnius.
- Audio/Visual Tutorials for Vergil's Hexameter, by Dale Grote, UNC Charlotte.