Words are the building blocks of human communication and provide a strong foundation for the development of skilled language production and comprehension. Learning words in a language other than one's own requires long-term commitment and substantial engagement. This research monograph offers a summary of how learners of additional languages acquire vocabulary in instructed foreign language contexts and in English for Academic Purposes programs in the target language environment. After a thorough introduction of the most important constructs in the first chapter, the book provides a comprehensive description of the processes of longitudinal development in learners' growth of vocabulary size and depth of word knowledge. In the second half, the authors make novel connections between the fields of second language acquisition and vocabulary research. They then show how individual differences between learners can influence the processes and outcomes of vocabulary learning. The book concludes with evidence-based practical guidance to language teachers on how to enhance their students' lexical knowledge.

IntroductionChapter 1. Defining and describing key constructs: Vocabulary and the mental lexicon1.1 Defining the concept of vocabulary1.2 Conceptualizing vocabulary knowledge1.3. Defining breadth of vocabulary knowledge and vocabulary size1.4. Definitions of depth of word knowledge1.5. Storing vocabulary knowledge: The concept of the mental lexicon1.6. What kind of information does the mental lexicon contain?1.7. Is the mental lexicon language specific?1.8. How is the bilingual mental lexicon structured?1.9. SummaryChapter 2 Longitudinal developments in the breadth of vocabulary knowledge2.1. Measuring vocabulary size2.2. Development of the breadth of vocabulary2.2.1. Patterns and profiles of development2.2.2. The development of recognition vocabulary size2.2.3. Comparison of the development of recognition vocabulary size in an intensive foreign language learning context and in an English for Academic Purposes programme in the UK2.2.4. The development of recall vocabulary size2.2.5. Comparison of the development of recall vocabulary size in instructed foreign language and target language contexts2.2.6. Vocabulary size in relation to proficiency levels2.2.7. Rate of development2.2.8. Comparisons of development in recall and recognition vocabulary size2.3. The role of word characteristics in the development of vocabulary size2.4. SummaryChapter 3 Longitudinal development in the depth of vocabulary knowledge3.1. Measuring depth of vocabulary knowledge3.2. Investigating depth of vocabulary knowledge using stimuli word lists3.2.1. Research method for a study on the development of depth of vocabulary knowledge of pre-intermediate learners of English3.2.2. Analysis of depth of word knowledge3.2.3. Development of depth of word knowledge of pre-intermediate learners3.2.4. Developmental order for depth of word knowledge types3.3. Investigating depth of word knowledge using tests of vocabulary associations3.4. Investigating depth of word knowledge by means of free production tasks3.5. SummaryChapter 4 Longitudinal developments in the organization of the second language mental lexicon4.1. Using word associations to analyse the mental lexicon4.2. Word associations in second language acquisition research4.2.1. Comparison of native and non-native associations4.2.2. Exploring the mental lexicon through word associations4.3. Investigating pre-intermediate learner's mental lexicon by means of word associations4.3.1. Developments in the organisation of the mental lexicon of pre-intermediate learners4.4. Comparison of the development of word associations in foreign and second language contexts4.4.1. Results of the study4.4.2. Discussion of findings4.5. SummaryChapter 5 Second language learning and vocabulary development5.1. Incidental and intentional vocabulary learning processes and conditions5.2. Implicit and explicit vocabulary knowledge and learning5.3. The role of input in vocabulary development5.4. The role of noticing in vocabulary development5.5. Encoding lexical knowledge in long-term memory5.6. Output, interaction and vocabulary development5.7. An overview of vocabulary development from the perspective of Dynamic Systems TheoryChapter 6. Individual differences in vocabulary development6.1. The construct of working memory6.2. The relationship between working memory and vocabulary development6.3. Motivation, self-regulation and vocabulary development6.3.1. Initial motivational conditions in vocabulary learning6.3.2. The actional stage of motivated vocabulary learning6.3.3. The post-actional phase of motivated vocabulary learning6.4. SummaryChapter 7 Research implications for vocabulary teaching7.1 Lexical space: breadth, depth and fluency7.1.1 Lexical breadth7.1.2 Lexical depth7.1.3 Lexical fluency7.1.4 The link between lexical breadth, depth and fluency7.2 Incidental vocabulary acquisition7.3 Explicit vocabulary instruction7.3.1 The role of different types of input7.3.2 The role of rich exposure and output tasks7.3.3 The role of task-based teaching7.4 Teaching formulaic sequences7.5 The interdependence of vocabulary and grammar7.6 Vocabulary instruction in the context of mobile learning7.7 SummaryReferencesAppendices