Mother tongue refers to the first language learned at home in childhood and still understood by the individual.
Home language refers to the language spoken most often or on a regular basis at home by the individual.
Knowledge of official languages refers to the ability to conduct a conversation in English only, in French only, in both English and French, or in neither English nor French.
Knowledge of non-official languages refers to languages, other than English or French, in which the respondent can conduct a conversation.
Language of work refers to the language used most often or on a regaular basis at work by the individual.