In the previous blog on this topic, I presented some information about the history of these two forms of the ‘same word’, which have exactly the same meanings.
Once a presumed synonym comes into existence, though, it seems that some people will search heaven and earth to find a justification for its existence. Such is the case with discernable. If you google it, you might be directed to Wikidiff, which assures you that there is a meaning distinction between the two forms. You could have fooled me, but here, for what it’s worth, is what that august fount of knowledge claims:
‘The difference between discernible and discernable is that discernible is possible to discern while discernable is detectable or derivable by use of the senses or the intellect.’
Whoever thought that up had not quite worked out that nonsense on stilts is still nonsense, even if stamped with the faux seal of the internet/Wiki/wotevah. If something is ‘possible to discern’ it can ‘be discerned’, which means that it is ‘detectable by use of the senses or the intellect.’ I’m not sure where the ‘derivable’ comes in, but this cyberjobsworth was clearly not averse to circularity.
According to the OED, whose judgement I prefer to that of Wikidiff, and according to common sense, whose virtues may be even greater than those of that august cultural monument, there is simply NO DIFFERENCE (at least in meaning) between the two words. Each has five senses, which are exactly paralleled in the other, including the fifth and obsolete ‘capable of discerning’ (an ability the writer of Wikidiff clearly lacked):
1603 S. Daniel Panegyrike sig. B3 God..Hath giuen thee all those powers of worthinesse, Fit for so great a worke, and fram’d thy hart Discernible of all apparences.
1650 Man in Moon No. 37. 295 I hope this will be a sufficient caution for all discernable, or rationall men.
The difference is a simple orthographical one, ‘derivable’ or ‘possible to discern’ by looking at data. Which is more frequent? Discernible or discernable. You know the answer yourself, vermute ich, but here is the science:
Figures and ratios for discernable/ible in several corpora:
Oxford English Corpus:
Feb 2014 – General – 4430/1472; total = 5,902; Ratio 75:25%
Monitor corpus Aug. 2017 – 9750/1861; total = 11,611; Ratio 83.97:16.03%
Academic journals, June 2015 – 6,303/1,858; total = 8,161; Ratio 77.23:22.77%
Corpus of Historical American (CoHA)– 1132/54; total = 1,186; Ratio 95.4:4.6%
NOW Corpus (News) – 5602/932; total = 6,534; Ratio 85.7:14.3%
Corpus of Contemporary American (CoCA)– 1096/190; total = 1,286; Ratio 85.2:14.8%
And here are the figures from the Global Corpus of Web-based English.
As you will have noticed, for most corpora, the proportion of discernible seems to hover betwen the 75% and 80% mark.
The exceptions are those datasets that exceed the 80% mark, of which there are four: OEC Monitor, CoHA, NOW and CoCA. To what extent the difference is signficant, not being a statistician, I am afraid I cannot say. The very high 95.4% of the CoHA data, though, is presumably due to writers historically being more careful about putting down what they thought of as the correct form.
Good ole’ Ngrams shows a slight drop in discernable at the beginning of the 19th century, and then an upward trend towards 2000, while discernible shows an earlier peak, and then decline.
Finally, omniscient Google asks ‘Did you mean discernible?’ if you key in the –able form.
So, yes, according to what the sources tell us, discernable is used and legitimate, but still a minority taste (a bit like the British LibDems, really). The only usage note I can find on it is in Pam Peters’ Cambridge guide, where she suggests that writers use the -able form either ‘in deference to the older tradition, or by using the regular English wordforming principle for English verbs’.
In that regard, the OED lists about 3,700 –able adjectives compared with a mere 600 for –ible.