How can we pronounce words ending with -sts?
I often heard people pronunce its like,
- lɪsts and kɒsts
- lɪsː kɔsː
but which one is acceptable?
In rapid speech particularly, consonants in clusters such as /sts/ are frequently lost in a process known to phoneticians as ‘elision’. Similarly, ‘next’ will occur as /neks/ and ‘acts’ as /aks/. It’s not so much a matter of bad pronunciation as a recognized feature of speech which most of us will display at one time or another.
Imagine the conversation, over a bad phone line.
Alice: Let's talk about the kɒsː associated with with this project
Bob: I'm sorry, "Coss"?
Alice: No. kɒsts. C.O.S.T.S.
Bob: Ah, sorry, you were speaking too quickly.
These are simple words that are said as they are written -- nothing to catch us out as with trough and plough.
But in English, as I believe with almost every language, people tend to rush over words. This is how going to becomes gonna.
So, it's kɒsts and lɪsts, when spoken by the Queen or a newsreader, but the t might disappear in everyday conversation.
The accepted pronunciation of '-sps', '-sts', and '-sks' is to drop the stop, and the 's' may or may not be extended (as though it were a doubled s). It is not frowned upon at all to not pronounce the p, t, k, even in slower speech.
In expected-articulate speech, say newscasters and actors, there will be a tendency to not drop.
lɪsts and kɒsts definitely. The others are just bad pronunciation.