Hello! My name is xxx. Im from argentina. I wanted to know when i should use the ju: and ju. It has to do with the vowel or consonat followed?
It’s difficult to know how best to answer this kind of query. The grammatical and spelling errors (reproduced here without correction) make it clear that the person making the query has not achieved a very high standard of English, nor indeed of literacy.
What does she mean by asking when to “use” juː and ju? If she wants to know which words I would transcribe with one and which with the other, the simple answer is to look them up in the dictionary. Possibly, though, the query is a more abstract and sophisticated one: how do I determine when to write one, and when the other. The brief answer to this depends on the distinction I draw in English between strong vowels and weak vowels.
Weak vowels are the vowels that can result from the weakening of strong vowels. They are found only in unstressed syllables. The English weak vowels are i, u and ə), plus sometimes ɪ and ʊ.
So if the vowel we are concerned with is in a lexically stressed syllable, we must write it juː — for example beauty ˈbjuːti, acute əˈkjuːt, amusement əˈmjuːzmənt. The same is true if it is in a strong (though unstressed) syllable: for example avenue ˈævənjuː, attitude ˈætɪtjuːd.
You will find ju only in a weak syllable. Examples include valuation ˌvæljuˈeɪʃən and stimulation ˌstɪmjuˈleɪʃən (though in the latter you can also get jə as the weak vowel, thus ˌstɪmjəˈleɪʃən). If the preceding consonant is an alveolar plosive, the j element usually coalesces with it to give a palato-alveolar affricate, as in situation ˌsɪtʃuˈeɪʃən: that is, tju→tʃu. In words where weak (j)u is followed by ə, for example annual ˈænjuəl, Samuel ˈsæmjuəl, the two vowels may combine into a diphthong, and there may be further vowel reductions. Study the entries for words such as actual(ly), gradual(ly).
Or perhaps the query is still more sophisticated, and is triggered by the fact that I transcribe jʊ in stimulus ˈstɪm jʊl əs but ju in stimulate ˈstɪm ju leɪt. This is a by-product of my analysis of syllabification, and I find that in my own pronunciation and that of many others that the back weak vowel is not as tense/high in closed syllables as it can be in open syllables.
But that isn’t something I want to try to explain to someone who not only confuses ‘following’ with ‘followed’ but doesn’t even know how to formulate a yes/no question in English.
At an elementary or intermediate level you can achieve a perfectly acceptable standard of English pronunciation by totally ignoring the distinctions I draw between strong uː, strong ʊ and weak u, ʊ. After all, millions of native speakers (those who come from Scotland and Ulster) ignore them.