What’s a glomerulus? I imagine most of us would have to confess that this word is not part of our vocabulary, unless we have a particular interest in disorders of the kidney.
According to the Concise Oxford Dictionary, a glomerulus is ‘a cluster of nerve endings, spores, or small blood vessels, esp. of capillaries at the end of a kidney tubule’. Wikipedia explains it more succinctly as ‘a capillary tuft that performs the first step in filtering blood to form urine’.
More relevantly for today’s blog, how do we pronounce this word?
It’s not in LPD or CPD. But COD tells us that it is ɡlɒˈmɛr(j)ʊləs. ODP, from the same stable, agrees, while using its special weak-vowel symbol ᵿ (U+1D7F, LATIN SMALL LETTER UPSILON WITH STROKE), which your browser may or may not be able to display.
Why the bracketed (j)? Why is the palatal element optional or variable?
There’s something awkward about the sequence rj. We long ago dropped the yod that presumably once existed in words such as rude (rɪud → rjuːd → ruːd), brew, true and so on, where the vowel is strong. The awkwardness arises in words where the vowel is weak. The yod tends to be preserved in weak syllables. The two best-known words that exemplify it are virulent and garrulous.
In the case of virulent, both LPD and EPD prefer the yodless ˈvɪrʊlənt for BrE, while also listing variants with -jʊ-, -jə- or -ə- between the liquids. For garrulous they both prioritize ˈɡærələs, but aɡain also admit variants with a yod.
Introspecting, I feel that in slow careful deliberate speech I want to include a j in these two words, and hence by extension in glomerulus. But in faster or less studied speech it’s too much of an effort to articulate the rj sequence, so I drop the yod.
Strangely, this does not apply if the -rj- derives from the compression of ri-, as in disyllabic glorious, merrier, variant. (See this blog for 16-17 January 2007.) In cases like these there is no tendency whatever to omit the palatal element.