I remain encouraged by yet slightly skeptical of all of these. I think there needs to be a better understanding of how (and even whether!) people come to understand themselves as multi/plurilingual and especially as monolingual. I've said before that applied linguistics may need a "monolingual studies" analogous to "whiteness studies" in other fields, but that might be a bridge too far...
Coste, Moore, Zarate: multilingualism describes societies, plurilingualism describes peoples' use of language.
the focus on the individual as the locus and actor of contact encouraged a shift of terminology, from multilingualism (the study of societal contact) to plurilingualism.
Moore: plurlingual and translingual are basically the same thing and are described in opposition to multilingualism which describes "separate competences in fixed and labelled languages"
Plurilingualism does not describe separate competences in fixed and labelled languages, but views languages as ”mobile resources” (Blommaert, 2010, p.43) within an integrated repertoire (Lüdi & Py, 2009) that can include translingual practice (Canagarajah, 2013).
Canagarajah - Translingual practice is an umbrella term which describes a number of 'newer' approaches to language that deviate from traditionally monolingually-oriented linguistics; a translingual orientation is therefore in opposition to monolingual orientation. (I would imagine that he and perhaps others would argue that the traditional understanding of "multlilingual" is actually based on a monolingualist orientation to language.)
I adopt the umbrella term translingual practice to capture the common underlying processes and orientations motivating these communicative modes.
Taylor & Snoddon - these terms are basically all the same -- plurilingualism, translingualism, polylanguaging, and even multlilingualism are all ways of describing the trend of embracing "other languages" in TESOL.
The time is ripe as there is a palpable zeitgeist and related (if separate) manifestations of plurilingualism, whether they are termed thusly or as translingualism, polylanguaging, or simply multilingualism. Indeed the four books reviewed in this special issue....all touch on various aspects of, and research on, the role and value of learners' and teachers' first languages and additional languages, and policies that support plurilingual repertoires in relation to English teaching and learning. We hope practitioners and researchers alike will find much on offer here to enhance their understanding of language teaching and learning.