The acquisition and pedagogical treatment of vocabulary in second language learning hinges on a nuanced understanding of lexical scope, frequency, and utility, affirming that vocabulary is both the foundation and the conduit of linguistic competence. Rather than aiming for the full lexicon of a native speaker—estimated at 20,000 word families—effective instruction prioritizes a high-frequency core of approximately 2,000–3,000 word families, which accounts for around 80–90% of typical textual coverage in English. These foundational units enable basic comprehension and are essential for reaching a threshold of linguistic autonomy, particularly when reading unsimplified texts. The role of word frequency lists, such as West’s General Service List (GSL) and the University Word List (UWL), is central in identifying which lexical items to target for maximum return. The research underscores that extensive reading and incidental learning—supported by targeted strategies like word cards and contextual guessing—can significantly expand vocabulary size, although initial direct instruction in core lexicon remains indispensable. Emphasis is also placed on form-focused instruction, word family recognition, and the critical role of multi-word expressions in fluency. Importantly, vocabulary acquisition is not linear but cumulative and stratified, with different learners requiring tailored pathways depending on their educational and communicative goals. Ultimately, vocabulary is presented not as a passive repository of memorized terms but as an active, structured, and strategic domain in language education that requires deliberate design, ongoing assessment, and a balance between repetition, variation, and contextualization.
