How did monolingual bias emerge and why does it persist? What are the epistemologies concerning human language? How do language and languages develop? What do the terms monolingual, bilingual, and multilingual mean? What does “typical” language development entail? What constitutes “atypical” language development? To answer these questions, this paper foregrounds that language is a human cognitive skill for communication, and that Anglo-American and European notions of language diversity, monolingualism, bilingualism, and multilingualism disseminate monolingual bias. Monolingual bias extends to educational and clinical contexts where children from bi/multilingual households and/or communities face inappropriate scrutiny when language practitioners assess and support them based on normative monolingual expectations or standards. Monolingual bias is then linked to conceptual issues on “typical” and “atypical” language development. Ultimately, this paper attempts to explain why Anglo-American and European notions of bi/multilingualism are less relevant for most, if not all, of the world’s multilingual contexts, especially in the Philippines.