This chapter examines the lexical availability of students of Spanish as a foreign language (SFL) and observes how their semantic networks change as their proficiency in Spanish increases. The analysis focuses on 150 students with different levels of proficiency and the two centres of interest: acciones y actividades habituales (‘Common actions and activities’) and aspecto físico y carácter (‘Physical appearance and character’), using specific tools to study lexical centrality. The aim is to determine whether there are differences in total word count, lexical cohesion, semantic network structure and available vocabulary in relation to proficiency level. The results show that the proficiency level has a decisive influence. An increase in proficiency level–especially when comparing beginners with intermediate and advance levels–results in a higher number of words, higher cohesion, and a denser, more interconnected network, consisting mainly of relationships based on type of activity, temporal order, antonymy and parasynonymy. In terms of differences in available vocabulary, the results confirm that students provide a wider range of vocabulary as they become more proficient. These findings highlight the importance of adapting SFL vocabulary teaching and suggest the need for further research into changes in vocabulary in different grammar and language proficiency contexts.