Over the last two decades, the literature on bilingual children has shown that children who grow up learning two languages do not typically differ in their total vocabulary size compared to their monolingual peers (Poulin-Dubois et al, 2012) though composition may be smaller compared to size with two word-forms representing one lexical concept. However, these studies often sample children from minority bilingual communities (Bialystok et al, 2010) where the languages may be used in somewhat separate contexts. By contrast, in Singapore more than 90% of young people are bi-/multilingual, and dense inter-generational community-level multilingualism is the norm. The education system has an active policy of bilingualism and the majority of children grow up in households where they hear two or more languages/dialects (forthcoming). In recent years, English has become the most frequently reported main language at home for children between ages 5-10 (2010 Singapore Census) indicating rapid language change. This language environment provides a unique opportunity to investigate individual differences in vocabulary development in a non-WEIRD massively multilingual community. \nUsing archival data from the longitudinal birth cohort ‘Growing up in Singapore Towards Healthy Outcomes’ (GUSTO), we investigated the size and linguistic composition of the expressive vocabularies of 140 24-month-olds whose parents filled out local adaptations of the MacArthur-Bates CDI in Mandarin and English. \nIn terms of composition, we find that the proportion of lexical concepts that a child can express in both their languages makes up 40% of their lexicon (Range: 5-537). The bias towards English language dominance is evident (Fig 1), but even the most extreme children are reported to have no more than 50% of their lexicon coming from only a single language. \nRegarding vocabulary size, pooled across languages, vocabulary size ranged from 8-760 (25th, 50th, 75th percentile: 67, 179, and 271 word-forms respectively). These values are notably lower than reported vocabulary sizes for age-matched samples in OECD countries like the UK, North America, and Australia (Oxford CDI, English (American), French (Quebecois), and English (Australian) versions of the Mac-Arthur Bates CDI, Wordbank, 2019). This mismatch is surprising given Singapore’s rankings in standardized educational assessments such as the PISA (OECD, 2018), and suggests that the current assessment tools may be missing an important part of children’s linguistic repertoire. \nIn response to this finding, our multilingual team has identified an entire tier of child-directed words that is not captured in vocabulary inventories adapted from monolingual materials. Many of these local-words aren’t easy to identify as belonging to one language or another (e.g., ‘pom-pom’ for ‘children’s bathing’) and likely arose from Singapore’s dense contact language environment where language mixing and translanguaging are normative. Without any national dictionaries for Singapore, this special tier of child-directed words exist mainly in oral language and have yet to be documented. In response to this finding, our current work includes collecting age of acquisition estimates for over 200 core local words, and developing a new vocabulary assessment to help discover how cheem (profound) the vocabularies of tiny Singaporeans really are.