An alphabet is a complete list of phonemes.
Alphabets, along with
abjads,
abugidas,
syllabaries, and others, are just a type of script, used for writing. Glyphs found in an alphabet may or may not correspond with the sounds produced by the mouthflaps of speakers of the language that uses the alphabet for writing. I mean, just look at English orthography; it's horrendous. And don't even think about looking at French orthography; it's appaling.
The International Phonetic Alphabet is an attempt at making a universal human alphabet that could accurately transcribe all the sounds possible to be produced by the human speech apparatus, regardless of the many spelling conventions used by different languages. It's meant to be complete, as in it includes even theoretical sounds that could be produced, yet have yet to be found in a naturally occurring language anywhere in the world. Tom Scott did a really good job of explaining the concept in
this video.
Now, the IPA is not just glyphs, that are meant to represent sounds that differ in their quality, but it also features symbols that can inform you how to group the sounds into syllables (
.), which syllable is stressed (
ˈ), or even which vowel's length is extended (
ː). Not all dictionaries and textbooks make use of all the features of the IPA for the sake of simplicity and making it accessible to learners who may not be familiar with them, but I think I've always seen
ː used as a mark that denotes that the vowel is meant to be pronounced as a long vowel. This means that the only difference between /u/ and /u:/ is the length; the quality is exactly the same. The difference between /u/ and /ʊ/ is the quality, not the length. Hence, different glyphs are used to represent these two sounds.
If I'm not mistaken, these two sounds are distinguished by length:
| ʊ | good /gʊd/, could /kʊd/ |
| uː | food /fuːd/, group /gruːp/ |
That is if you need a sound with the same articulation but shorter, it will be /ʊ/, not /u/.
That is incorrect. /uː/ and /ʊ/ are different in their quality. If you can't tell the difference in quality between /uː/ and /ʊ/, and only notice the difference in length, it's because you're a learner and you haven't trained your ears enough to catch that difference yet. Perhaps you should spend some time practicing minimal pairs, such as
fool and
full, or
pool and
pull. Once you can tell the difference between the quality of these sounds, you should be able to tell /u/, /uː/, and /ʊ/ apart.
Now that I'm thinking about it, I'm not sure if /ʊː/ is a thing in English. Is it, 5jj?
