 Liaison is most generally defined as the smoothing out of syllable boundaries in speech by adding a phoneme that is not heard in isolation. Let us identify the linking phonemes on the basis of a sentence read very carefully. The aroma of tea greeted you as you entered our office. Using liaison effects this sentence can alternatively be read as the aroma of tea greeted you as you entered our office. Thus we can identify three linking phonemes in present-day English. Yeh, where a final high front vowel precedes another vowel. Wa, where a high back vowel precedes another vowel. And the insertion of R. In each case the additional phoneme bridges the gap between two vowels. In present-day English liaison on a phonemic level is mostly associated with the use of R in this context. There are two variants of this R liaison in present-day English. In cases of linking an orthographically present and phonemically final post vocallic R is pronounced when the next word starts with a vowel. So we get cases such as here in London. Since American English is highly rotec linking is a standard feature of it anyway. The phenomenon of intrusion or the intrusive R is confined to the non-rotec varieties of English. Here the phoneme R is inserted between two vowels even if it is not represented orthographically. The condition is the final vowel of the first item must be a low back or a central vowel. And the next word must start with a vowel. So in RP we get low end order and so on. Similar to the other connected speech effects such as assimilation and delusion liaison is mainly optional.