Tutorial on word stress

In the examples below, word stress is indicated by an apostrophe preceding the stressed syllable.
Periods indicate syllable boundaries.
Equal signs indicate morpheme boundaries.

Germanic stress rule

Since English is a Germanic language, English words were originally subject to the Germanic stress rule in (1).

(1)     Germanic stress rule:
Germanic words consist of a stem, preceded and followed by optional unstressable affixes. Word stress falls on the stem-initial syllable.

(2) a. Stem-initial syllable is word-initial
'hea.ven
'lat.ter
'un.der.=ling
b. Stem-initial syllable is not word-initial
for.='get
mis.='take
mis=un.der.='stand
un.der.='stand
with.='draw
c. Exceptions (very rare)
e.'le.ven

French stress rule

As a result of the Norman Conquest in 1066, many French words entered English, whose stress originally followed the rule in (3).

(3)     French stress rule:
In French, word stress falls on the final stressable syllable of the word. Syllables containing schwa are unstressable, and word stress falls on the immediately preceding syllable. Schwa is spelled as syllable-final e, and the unstressable syllables are parenthesized in what follows. Syllable-internal e is stressable.
(4) a.   Final syllable is stressable cas.'tel
pen.'dant
tes.ta.'ment
b.   Final syllable containing schwa is unstressable ad.ven.'tu.(re)
a.'zu.(re)
ma.ri.'a.(ge)
'ta.(ble)

A complicating factor

Stress on verbs borrowed from French (and from Romance more generally) tends to remain on the stem, as illustrated in the morphologically related noun-verb pairs in (5). Given our focus on stress shift, we will exclude verbs from consideration for the purposes of the class.

    Noun Verb
(5) a.   'ad.mit ad.'mit
b.   'con.voy con.'vey (near-minimal)
c.   'in.cense in.'cense
d.   'per.mit per.'mit

Latin stress rule (= Quantity Stress Rule)

Starting in Old and Middle English, but particularly after 1500, English borrowed many words from Latin. This fact is relevant for our project because many words that were in actual fact borrowed from French (at least as far as the editors of the OED are able to ascertain) might in principle have been borrowed from Latin instead. Just looking at a particular word, there is no way that a speaker, either now or then, could tell which language is the immediate source of the borrowing.

Stress in Latin was based on syllable weight or quantity.

(6) a.   Closed vs. open syllable:
If a syllable ends in at least one consonant, it counts as closed.
Otherwise, a syllable counts as open. There are some complications to this straightforward system: First, in words with s + stop, the syllable boundary was between the s and the stop (for instance, au.gus.tus rather than au.gu.stus). Second, syllable boundaries involving stops and liquids were ambiguous (at least in Latin verse) and could count as open or closed.
b.   Heavy vs. light syllable:
A closed syllable or one containing a long vowel or diphthong counts as heavy.
Otherwise, a syllable counts as light.
Another way of making this distinction is in terms of moras (one mora = light; more than one = heavy).
c.   Latin stress rule:
Word stress falls on the penultimate syllable if it is heavy; else, on the antepenultimate if available; else on the penultimate.

Heavy penultimate (long vowel or diphthong) di.'vī.nus 'divine'
hu.'mā.nus 'human'
im.pe.'rā.tor 'emperor'
li.ber.'tā.tis 'liberty, gen. sg.'
ser.vi.'tū:.do 'servitude'
Heavy penultimate (short vowel with following consonant(s)) au.'gus.tus 'august'
Ka.'len.dae 'Calends'
li.'ber.tas 'liberty, nom. sg.'
Light penultimate 'ca.pi.tis 'head, gen. sg.'
'Iū.li.us
'op.pi.dum 'city'
pe.'ri.cu.lum 'danger'