Double consonants in English: Graphemic, morphological, prosodic and etymological determinants

– ; but also – ). So the functional motivation to discern word pairs is far greater for monosyllabic roots.

One final (minor) sub-regularity: In British English, is doubled even in cases where it is unstressed/not a monosyllabic root (15a); in American English, it is not (15b) (cf. e.g. Carney 1994: 251).

(15) a. , ,
b. , ,

In British English, one consonant thus behaves oddly; American English is more coherent in this respect (but cf. Brame 1983a,b)

3.2. Derivation

Products of derivational word formation rules also comply with the constraint (5) and the morphological hypothesis. This holds for the doubling (16a) resp. non-doubling (16b) of consonant letters in the following words:

(16) a. , , , , , ,
b.
, , , ,

In the cases in (16a) and similar cases, the stem ends with a monosyllabic root, and the final consonant letter is doubled. The cases in (16b), on the other hand, involve polysyllabic roots and show single stem final consonant letters.

There are only a handful of exceptions in CELEX. A number of words occurs with unexpected -doubling (e.g. , ,
, ). As noted above for inflected words with , this seems to be a case of diatopic variation, with British English favouring the -forms and American English favouring the -forms. The other exceptions involve unexpected single consonants (17a) or unexpected doubling (17b):

(17) a.
, ,

b. ,

According to both the prosodic and the morphological hypothesis, we would expect consonant doubling in (17a) if the words are indeed formed on the bases par, gas, and scar. For gasify, the form was historically a variant as the OED notes, attested from the 18^th century onwards; it would be interesting to see whether this spelling still occurs (there are no instances of in CoCA, though). Scarify nicely captures the whole point of consonant doubling: It can be formed on two bases, scar and scare, and both meanings are attested, both with their own unique phonological form – but without consonant doubling, both senses and pronunciations collapse.

The two words with unexpected double consonants in (17b) are British spellings, as a comparison between CoCA and BNC shows: The -forms are the dominant ones in the BNC, while the -forms are the dominant ones (in fact the only attested) in the CoCA.

The number of words with double consonants varies greatly between suffixes. For example, there are 212 words with consonant doubling followed by in CELEX (etc. , , ), but only four words with consonant doubling followed by (, , , ). At first glance, this appears to be a feature of suffixes – -er occurs with double consonants, -ance only marginally does so. But the reason for this may very well be morphological: If the suffix operates on monosyllabic bases, the amount of consonant doubling is higher; if it operates only on polysyllabic bases, the amount is smaller.

Finally, independent of whether the prosodic or the morphological hypothesis is preferred, there seems to be a constraint relating all double consonants in derived words to stressed syllables before the corresponding consonant phonemes. This usually holds in cases like (18a), but not in those in (18b, cf. also Cummings 1988: 169):

(18) a. , ,

b. *, *, *

The forms in (18b) should be preferred on the grounds of both the prosodic and the morphological hypothesis: the stem has final stress, and the stem contains a final monosyllabic root (fer). Yet it is unclear how systematic these spellings are. They are certainly exceptions within the set of -ence and -able formations. The reason for the spellings in (18b) may be thought to be prosodic: After all, the double consonants wrongly indicate word stress on the second phonological syllable. But this explanation does not hold for a number of other words: In e.g. , ,

, , and , the ult is stressed, not the penult (as the double consonants indicate). For the time being, I will treat the spellings in (18b) as idiosyncratic.

4. The periphery: Monomorphemic words

In monomorphemic words, consonant doubling is much less regular. The first class of words are of Latin origin. They are not strictly monomorphemic, but they are not unequivocally morphologically complex either; they are composed of a Latin prefix and a Latin stem, e.g. those in (19):

(19) collect, command, correct, connect, illegal, immersion, innate, comment

In these cases, the vowel letter before the double consonant corresponds to a short vowel phoneme, but it is mostly not stressed (there are exceptions like comment, however). To capture this distribution, one can list prefixes that often correlate with consonant doubling. The following list is from Rollings (2004: 83):

(20) ad-, con-, dis-, in-, ob-, sub-

Additionally, assimilations in the original Latin words have to be accounted for as well (ad + facere => affect, in + mobilis => immobile). The biggest problem for writers, however, is that at least some etymological knowledge seems to be required to predict these double consonants (cf. e.g. Carney 1994: 119ff., Rollings 2004: 83f.). Without it, the spellings (at + one) and (ad + tangere) are purely idiosyncratic. There may be certain distributional cues (cf. Carney 1994: 120, Rollings 2004: 84), but on the whole, some knowledge about word origin seems to be required.

Apart from words with Latin prefixes, the most important observation is that consonant doubling is highly correlated with the graphemic shape of the word ending¹⁰. A review of the pertinent literature leads to the inventory in (21a) (examples in 21b) for those word endings that occur with double consonants and the inventory in (21c) (examples in 21d) for those that follow a single consonant (Carney 1994: 116f; Rollings 2004: 81f):

(21) a. <-ic>, <-id>, <-it>, <-ish>, <-ace>, <-ous>, <-al>, verbal <-age>, <-ule>

b.
, , ,
,
, , ,
c. <-et>, <-ow>, <-y>, nominal <-age>
d. , ,