1. Digging into dominance: a closer look at language dominance in bilinguals Carmen Silva-Corvalan and Jeanine Treffers-Daller; 2. Dominance and proficiency in early and late bilingualism Silvina Montrul; 3. Related but different: the two concepts of language dominance and language proficiency Anika Schmeisser, Malin Hager, Laia Arnaus Gil, Veronika Jansen, Jasmin Geveler, Nadine Eichler, Marisa Patuto and Natascha Muller; 4. The complementarity principle and its impact on processing, acquisition, and dominance Francois Grosjean; 5. Dominance in bilingualism: foundations of measurement, with insights from the study of handedness David Birdsong; 6. Using lexical diversity measures to operationalize language dominance in bilinguals Jeanine Treffers-Daller and Tomasz Korybski; 7. Balance patterns in early bilingual acquisition: a longitudinal study of word comprehension and production Annick De Houwer and Marc H. Bornstein; 8. Amount of exposure as a proxy for dominance in bilingual language acquisition Sharon Unsworth; 9. The role of the childhood environment for language dominance: a study of adult simultaneous bilingual speakers of German and French Tanja Kupisch and Joost van de Weijer; 10. Assessing the relationship between input and strength of language development: a study on Italian-English bilingual children Francesca La Morgia; 11. Measuring language dominance in bilingual children: implications for cross-linguistic influence Elena Nicoladis; 12. Language dominance: the construct, its measurement and operationalization Jeanine Treffers-Daller; 13. Conclusion Jeanine Treffers-Daller.