English is the global default for the academic literature, for international trade, for cross-border professional services, and for most multinational employer communications across every subject on the taxonomy. International journals in every subject default to English. International conferences default to English. The default language of MNC employment in India, the Gulf, Southeast Asia and Latin America is English. The default language of trade documentation — bills of lading, letters of credit, certificates of origin, FTA preference declarations — is English with a local-language addendum.
But English is not universal. Manufacturing roles in continental Europe (Germany, France, Italy, Spain) often require local-language fluency at B2+ for shop-floor and supply-chain communication. Healthcare delivery in any country requires fluency in the language of the patient population. Legal practice in non-English jurisdictions requires the local procedural language. Public-administration roles almost always require the official language of the jurisdiction. Sales and customer-success roles in any market typically require the dominant local language.
School Is Cool's English view threads the 100 subjects through this English-as-default-but-not-universal reality. For each subject, it documents which professional contexts run cleanly in English, which require a local-language credential at what level (CEFR A2 / B1 / B2 / C1 / C2), and which language credentials are most credible in which destination.