The analogy to dock/duck seems fair, but I don't see why you don't want to call that an accent. Vowel troubles of that kind are a major feature of thick accents. Staying in the Chinese context, someone saying "fourth" in a thick Mandarin accent will actually say "force". (Depending on how thick; they'll probably say something more like "four-suh".) That's not because they're saying the wrong word -- they know what fourth means; they just can't say it.
In context, this kind of thing isn't a problem because a speaker with a heavy accent applies their own sound changes in a systematic way. It's very easy, as the listener, to learn their accent and adjust to it... if they're coming out with otherwise normal speech. As a foreign language learner, you probably have a thick accent _and_ you also can't form a normal sentence, so context can't provide the support it normally would for your odd pronunciation.
(If "dock" and "duck" were actually pronounced identically, that would cause no problems, in the same way that the identical pronunciation of "bow" (archery) and "bow" (decorative knot in a ribbon) causes no problems. That's most of why it doesn't matter if someone's accent causes them to pronounce some words as other words.)
As you say, a fluent English speaker with a thick Mandarin accent will understand and often hear the distinction between "fourth" and "force". They just can't easily produce /θ/ in their own speech. If someone's flashcards said both words have the same pronunciation, even if they know it's important to "adapt your accent as you speak", I'd definitely say they're learning incorrect pronunciation.
Sure, and looking up, I think the answer to the implicit question "Why are we supposed to memorize word tone in Mandarin when we don't need to memorize word stress in English?" is "You do need to memorize word stress in English. The details are up to you, but it's not optional."
But here, what I'm really asking is:
What's the difference between "saying the wrong word" and "saying the right word in a thick accent"? In my eyes, those appear to be the same thing, so I don't see how anything could be more like one than the other.
If someone said "strawBERry", for example, I would identify that as unambiguously being the right word. There is a canonically correct stress, and native speakers will notice when you get it wrong, but I wouldn't think for a second they might be talking about some other food I didn't know the word for. Even with the words where stress does carry meaning (content, object, etc.), I would identify them as a single word where context changes the pronunciation and meaning rather than two different words that happen to be written the same way.
> Even with the words where stress does carry meaning (content, object, etc.), I would identify them as a single word where context changes the pronunciation and meaning rather than two different words that happen to be written the same way.
Ah, this is where we disagree. In my view, the fact that strawBERry doesn't exist is just a coincidence. It's helpful in resolving what somebody meant by strawBERry, but not meaningful. The structure of English is compatible with a word pronounced strawBERry that means "barstool".
When I was a teacher in an English immersion school, I once asked a student if classes would be happening during a... holiday? I forgot why I thought they might not.
Anyway, the question was whether classes would be happening, and the student understood me correctly and responded "poss", leaving me confused.
He meant that classes were suspended, and he meant to say "pause", and he was aggrieved that the difference between the /z/ in "pause" and the /s/ in *poss meant so much to me when he thought it should be unimportant. But it was unimportant. The real problem was that the single word "pause" is not a valid response to that question in idiomatic American English. If it had been, I would have had no trouble understanding -- after all, there is no word "poss" to get in the way.
I see tone and stress the same way. Consonant choice / tone / stress are all parts of the word, and changing them gets you a different word.
In context, this kind of thing isn't a problem because a speaker with a heavy accent applies their own sound changes in a systematic way. It's very easy, as the listener, to learn their accent and adjust to it... if they're coming out with otherwise normal speech. As a foreign language learner, you probably have a thick accent _and_ you also can't form a normal sentence, so context can't provide the support it normally would for your odd pronunciation.
(If "dock" and "duck" were actually pronounced identically, that would cause no problems, in the same way that the identical pronunciation of "bow" (archery) and "bow" (decorative knot in a ribbon) causes no problems. That's most of why it doesn't matter if someone's accent causes them to pronounce some words as other words.)