Earlier today, I saw a question about phonetics:
When do I REALLY need to pronounce an s as a z?
Yeah, I know the rule that after a voiced consonant, the plural or 3rd person S should be realized as a Z. But I wouldn't trust that rule as far as I could throw it, because I constantly hear, say, 'problemsss' instead of 'problemzzz', or 'comesss' instead of 'comezzz'. What is the right pronunciation?
Unfortunately, this question was closed as "entirely answerable with a dictionary":
Basic questions on spelling, meaning or pronunciation are off-topic as they should be answered using a dictionary. See: Policy for questions that are entirely answerable with a dictionary
As I see it, there are two problems:
- This isn't a basic question!
- It can't be entirely answered by a dictionary.
The OP already knows what the rule for English genitive and plural allomorphy is, and they've stated it clearly in their question. Even if a dictionary tells them what the rule is, that doesn't answer their question, because they already know the rule. Their question is whether the rule is really accurate.
And it's a good question, too. Why? To answer that, we need to cover the difference between phonemic and phonetic transcriptions:
- A phoneme is a unit of sound the way a native speaker hears it and conceptualizes it mentally. For example, the words spin and pin both have the same /p/ phoneme. When native speakers hear either of these words, we hear the same sound. Dictionaries usually have phonemic transcriptions, so they'll list both of these words as containing a /p/ sound. That doesn't mean the /p/ sounds are physically identical; it just means that the native speakers don't distinguish any pair of words based on the difference, and they don't usually notice the difference themselves.
- On the other hand, there are phonetic details which a native speaker typically does not notice. In the word pin, there is a puff of air following the /p/ sound, but in spin there is no puff of air. This is important for learners, because they have to learn which /p/ sound to use in different phonetic contexts, or they'll sound strange to native speakers. They also need to learn these details because, in their own native languages, [p] and [pʰ] may be different phonemes, so they need to be taught explicitly that they're the same phoneme in English.
If you look up spin in a dictionary, which sort of transcription will you get? Almost certainly, a phonemic transcription. You won't find [pʰɪ̃n] and [spɪ̃n] in a dictionary; you'll find /pɪn/ and /spɪn/, because the phonetic details are predictable from the phonetic context and don't need to be listed. But the phonetic details are still important to learners, and they should be able to ask about them here without being told to find their answer in a dictionary.
So what about the question about plural/genitive suffix allomorphy? I'd like to avoid actually answering the question in this meta post, because this isn't where answers go, so instead I'll talk about a related issue that I've already posted an answer about, a phonetic process known as devoicing. First, let's look at a comment left on the devoicing question:
You can rely on the pronunciation presented by any dictionary, e.g. Collins. /dɪˈziːz/ is standard in both BrE and NAmE. The alveolar hissing sibilant is not heard, and even in the trailer you link to, it's not there to my ear. – P. E. Dant Nov 23 '16 at 0:01
In this comment, a native speaker wrote that he clearly heard a final /z/, just as dictionaries give the word. But the OP heard a final [s]. Neither of them is wrong, but how can we reconcile these two points of view? Again, we have to talk about not just phonemics, but phonetics. As I wrote in my answer:
The phoneme here is /z/, just as you'd expect based on the transcription available in a dictionary. That is to say, native speakers of English will definitely hear this sound as /z/.
However, you're quite right that you're hearing an [s] sound! The /z/ sound here has undergone a phonetic process known as devoicing, something native speakers generally don't notice (as you can see from the comments section on your question). With devoicing, the /z/ phoneme in this word is actually pronounced as [s].
And the native speaker who posted the first comment was surprised but convinced. He left a new comment to this effect:
Skeptics can visit this link, where they will find a clip of the word "disease" taken from the trailer; I have inserted .3 seconds of silence between the phonemes. The unvoiced sibilant is clearly heard at the end. – P. E. Dant Nov 23 '16 at 4:09
This kind of question is quite tricky, because at first glance the answer seems obvious to a native speaker. The dictionary says /z/, they hear /z/, and that's the end of the story! But it's really not. For a learner, this kind of question is quite challenging. They need to be able to find out if there are phonetic processes going on that they're hearing properly, or if they're simply hearing things incorrectly, and a dictionary cannot answer that sort of question.
When I saw that question about phonetics closed today, I took a moment to read it and decided to reopen it. I believe this question is valuable and has a place on ELL. I hope we can keep questions like this open in the future as well, and avoid using the "dictionary" close reason for cases like this, where it doesn't really apply.