Global multilingualism is undoubtedly increasing, yet some contexts are linguistically more diverse than others purely as a result of the nature of linguistically diverse communities and, by proxy, passive linguistic exposure that individuals may experience by being immersed in the contextual milieu. How the sociolinguistic context of language use contributes to an individual's linguistic repertoire has yet to be fully conceptualised or quantitatively investigated within the language sciences. To meet this goal, I first explore this overlooked contextual linguistic feature through the development, validation, and application of a holistic language profiling measure, the Contextual Linguistic Profile Questionnaire (CLiP-Q). To this end, three research studies are presented. First, I develop and validate a psychometric tool, the Contextual and Individual Linguistic Diversity Questionnaire (CILD-Q as part of the larger CLiP-Q), which measures multilingual exposure and endorsement as pertaining to particular linguistic contexts. From an exploratory factor analysis with data from 353 participants (62.9% South African, 37.1% UK), a three-factor solution best describes the structure of the CILD-Q: Multilingualism in Context (contextual use and societal practice of multiple languages within a community), Multilingualism in Practice (direct and indirect linguistic exchanges and conversational interaction), Linguistic Diversity Promotion (societal and governmental endorsement of linguistic variation). The CILD-Q positively correlates with a metric of the social diversity of language use (language entropy) further evincing its convergent validity, and item scores corresponding to the three factors have sufficient reliability (α’s > .80). Second, I apply the CILD-Q to evaluate whether people who live in a multilingual context (South Africa) report greater contextual linguistic diversity than those from a predominantly unilingual context (England), as well as evaluate the role of language entropy, lingualism status (monolingualism, bilingualism, multilingualism), socio-economic status, and code-switching practice on this effect. Results demonstrate that contextual linguistic diversity differs between nations with South Africans scoring higher. The promotion of multilingualism is dependent on SES only in the England group, where England participants with higher SES score higher on Linguistic Diversity Promotion. Lingualism status is not contextually comparable when measured categorically, and code-switching accounts for linguistic features of South Africans. Finally, a positive relationship emerged between language entropy and contextual linguistic diversity, suggesting complementarity between measures that capture the social influence of language experience. Third is the application of the CLiP-Q to contextualise and appropriately categorise the language experience of South Africans completing tertiary education to investigate high-level text comprehension ability. The ability to draw inferences from auditory and written input is crucial for comprehension and successful educational outcomes, and is especially relevant in linguistically diverse contexts where learners have heterogeneous language backgrounds but are educated in the predominant language of the country. Such a case is South Africa, where tertiary education is almost exclusively received through the medium of English, though it is not the first language (L1) for the majority of citizens. Accordingly, the third study assesses the role of language experience (L1, multilingualism, and contextual linguistic diversity) and inhibitory control on high-level listening comprehension in undergraduate multilingual South Africans with advanced English proficiency. Results indicate that L1-English participants were more efficient and accurate at monitoring and revising their listening comprehension, while participants with higher contextual linguistic diversity were less efficient at monitoring and less accurate at revising the comprehension content. Furthermore, individual differences in inhibitory control were associated with differences in revision where participants with lower inhibitory control took longer to update the content and replace their initial interpretation for a new one. Participants’ L1 appears to supersede their advanced English proficiency on highly complex listening comprehension involving revision. In this dissertation, I demonstrate that the CLiP-Q is a holistic instrument with which to measure and quantify contextual linguistic diversity which, in turn, is relevant to a range of higher order linguistic skills essential for academic development.