Ch#2 Language choice in multilingual communities

Here are some key points that I learned from reading chapter 2 of my sociolinguistics textbook (An introduction to sociolinguistics by Janet Holmes, second edition, 2001).
linguistic repertories: all the languages that one can use fluently
domains (a term popularized by an American sociolinguist Joshu Fishman): A domain involves typical interactions between typical participants in typical settings. Some examples of domain include 'family', 'friendship', 'religion', 'education', 'employment', etc.
If your community is monolingual, the term variety includes different dialects and styles of language.
Domain is clearly a very general concept which draws on three important social factors in code choice -- participants, setting, and topic.
People may select a particular variety or code because it makes it easier to discuss a particular topic, regardless of where they are speaking.
leakage: At home, people often discuss work or school, for instance, using the language associated with those domains, rather than the language of the family domain. Some describe this as 'leakage', suggesting it is in some way irregular -- the code associated with one domain is 'leaking' into another.