Googling around, I find people puzzled not only about the correctness or otherwise of “deteriate” but also about why this (mis)pronunciation should have become popular.
Deteriorate vs deteriate?And
I have checked the dictionary and I can't seem to find this word 'deteriate', but I hear all sorts of people say it and I assume (from what they are talking about) this word really is deteriorate.
So why do you think these people think deteriate is a word?
—I think it's probably just their accent or how they were raised to say it, because you're right "deteriate" definitely isn't a word. A lot of people I know say it and it's really annoying. You should just show them this link [to an on-line dictionary entry for “deteriorate”].
I forgive anyone making mistakes ..., but this pronunciation is not a mistake. It seems to be what a lot of people think is correct. What I wanted to know was, why?
So in this view a word “exists” only if it’s in standard dictionaries. And the word is its spelling.
And obviously the correct pronunciation is the one which follows the spelling.
There are difficulties with this popular view. No one would claim that we ought to say ˈkʌpbɔː(r)d for cupboard, although that is what the spelling suggests. No one argues that we ought to pronounce a w in wrong or a k in know. And what about words that have only just come into use, whether spoken or written, but are not (yet) recorded in dictionaries? How can we follow their established spelling, if they haven’t yet got one? (I imagine all would agree that the onus is rather on the lexicographers to bring their dictionaries up to date.) What about words such as the BrE scarper ‘run away, escape, make off in haste’, where it is pretty clear that the usual spelling reflects the (non-rhotic) pronunciation, rather than the other way round?
As for why people tend to simplify diˈtɪəriəreɪt to diˈtɪərieɪt, the answer must lie in the tendency to eliminate one of two adjacent identical consonants — the same tendency we see in ˈprɒb(ə)li for ˈprɒbəbli probably, ˈlaɪb(ə)ri for ˈlaɪbrəri library and so on. See my blog for 7 March 2007 concerning ˌsfɪɡməˈnɒmɪtə, and that for 1 Mar 2011 about ˈkwɒntətɪv.
This phenomenon is not dissimilation; the only term for it seems to be haplology.