/w/ is a labio-velar approximant/semi-vowel. The lips are rounded and the tongue is in the position for a back close mid / close vowel.[FONT="][/FONT]
The pronunciation of the approximant /r/varies considerably. in BrE RP, it is a post-alveolar approximant, IPA [[FONT="]ɹ[/FONT]]. It may also be rendered as an alveolar tap [[FONT="]ɾ[/FONT]]; in other vaieties it can be a lingual trill [r], an uvular trill [[FONT="]ʀ[/FONT]] or an uvular fricative [FONT="][ʁ[/FONT]]. It can also be [[FONT="]ʈ[/FONT]], aimilar to [[FONT="]ɹ[/FONT]], but with more reroflexion.
1.Is the word approximant just another word for semi-vowel?
2.Is this description correct for the sound /w/ in RP? /w/ voiced labio-velar approximant. Forget the 'voiced'. It can be at least partly devoiced after /t,k/, as in twin, quin, sqeeze.
3. Is this description of the sound /r/ correct in RP? /r/ voiced post-alveolar approximant Forget the 'voiced'; It's usually fully devoiced after voiceless plosive, as in pray, trend.
4. Is it correct to label the sound /r/ in RP rolled instead of approximant? No. The approximant /r/ may be rolled/trilled in RP in oratory, (and it often is in some varieties if Scottish English), but it is not usually trilled in RP
5. Do we have just one post-alveolar sound(r) and just one labio-velar(w) sound in RP?
/ʃ/ and /ʒ/ are post-alveolar fricatives.