| Definition -
A type of sandhi where changes occur at word boundaries, e.g. in English when we use an if the following word begins with a vowel and a if it does not.
As opposed to internal sandhi where change occurs at morpheme boundaries within words, e.g. in English, the plural suffix -s is pronounced as /s/ after voiceless consonants (e.g. cats) and as a /z/ after voiced consonants (e.g. dogs).