This study provides a comparative-theoretic account of code-switching in Azeri-Farsi-English multilingual communities in the USA and Iran. The salient differences between the grammars of these communities, I claim, reside in the relative ‘value’ each community places on the two relational constraints: POWER and SOLIDARITY.

I follow Bhatt and Bolonyai’s (2011) optimality-theoretic framework for the analysis of inter-community variation.

The data are drawn from over 15 hours of audio-recorded natural conversations among Azeri-Farsi-English multilingual speakers in Iran and the USA. The recordings were transcribed and coded for the five meta-pragmatic constraints of FAITH, FACE, SOLIDARITY, POWER and PERSPECTIVE proposed by Bhatt and Bolonyai.

The results reveal that despite overwhelming similarities in Azeri communities in the USA and Iran, the difference in their sociolinguistic grammars are significant, resulting from the interaction of SOLIDARTY and POWER. Crucially, in the diaspora context, SOLIDARITY outranks POWER, but in the indigenous context POWER outranks SOLIDARITY. I argue that this ranking difference between the two sociolinguistic grammars pertains to the practices that offer the profit of distinction (Bourdieu, 1991): in the diaspora context it is the solidarity function, accomplished by switching to Azeri and/or avoiding POWER switches, whereas in the indigenous context it is the differentiation function, in terms of status/power, accomplished through switching to English/Farsi.

A rather favorable consequence of the approach to code-switching I have adopted is that it allows us to capture the precise micro-discursive changes that are effected by mobility and displacement.

The theoretical approach followed in this study has implications for a sociolinguistic theory of mobility; that changes in sociolinguistic behavior under movement (diaspora) are, in fact, predictable: I argue that the enhancement of the value of solidarity vis-à-vis power as a result of migration is a predictable sociolinguistic behavior similar to other diasporic communal activities.