Introduction
Vocabulary development is an important part of developing all students' literacy, enough so that it is considered one of the five main components of literacy, along with phonemic awareness, phonics, fluency and comprehension. It would then be assumed that vocabulary would also be an important part of English as a Second Language (ESL) education, but this was not always the case. According to Choudhury (2010), the teaching of vocabulary as ESL content didn't come about until the 1980's and 1990's. ESL instruction from the 1940's to the 1960's focused on the Audio-Lingual Method, which viewed language as a primarily oral rule governed system (Choudhury, 2010). ESL instruction during this time period focused on grammar and pronunciation. This model dominated until the 1960's and 1970's, when linguists began to re-think the role of vocabulary and its importance. By the 1990's ESL theory focused on a lexical approach. Michael Lewis proposed that ESL instruction should include 'lexical chunks', or groups of words that are commonly found together. Lewis felt that "native speakers of English had a large store of lexical chunks which they habitually drew upon to produce fluent, accurate and meaningful language (Choudhury, 2010, p. 309). What followed was that teachers began to focus on lexical competence and the ability to apply words in various contexts. Therefore, the direct teaching of vocabulary as a component of ESL literacy is a relatively new approach that has prompted much scholarly research in recent years.
There is a great deal of research on developing literacy in children, but what constitutes best practices for mainstream students is not enough for English Language Learners (ELLs). Specific strategies for ELLs needed to be employed for students to become both orally and academically proficient in English. Research on reading has found that vocabulary knowledge affects reading comprehension, including "higher level processes such as grammatical processing, construction of schemata, and text models. Skilled readers can tolerate a small portion of unknown words in a text without disruption of comprehension and can even infer the meanings of those words from sufficiently rich contexts" (August et al, 2005, p. 50). Students with better reading comprehension have a better vocabulary, and vice versa. Interestingly it is the depth of vocabulary that has a greater affect on reading comprehension rather than breadth. Breadth of vocabulary refers to learning many different vocabulary words. Depth of vocabulary is that "knowing a words implies many things about the word- it's literal meaning, its various connotations, the sorts of syntactic constructions into which it enters, the morphological options it offers and a rich array of semantic associations such as synonyms and antonyms" (Carlo et al, 2004, p. 192). Students with depth of vocabulary not only understand the denotation, connotation and morphemes of a word, but that many words can be polysemous (have multiple meanings). Many ELLs not only lack depth of vocabulary, but more importantly breadth of vocabulary, which leads to lower levels of comprehension.
The learning of vocabulary can be either through incidental or explicit teaching. ELLs learn many vocabulary words over time incidentally, through listening and reading. Students that learn new words through incidental teaching need to be exposed to vocabulary words many times before they become part of their repertoire. ELLs that may benefit the most from incidental teaching are middle to advanced proficiency students that already possess strategies to decipher meaning from newly encountered vocabulary, either from text or oral language (Choudhury, 2010). Words that are encountered through incidental teaching tend to be more common, high frequency, or Tier I words, as opposed to more academic language (Tier II and III words). ELLs with a lower level of English proficiency need direct, explicit instruction of vocabulary words, as well as strategies to infer meaning from newly encountered vocabulary. All ELLs, whether beginning or advanced, need many opportunities to practice using these newly learned vocabulary words in a variety of ways to ensure comprehension.
Vocabulary Strategies and Best Practices
Learning academic language and vocabulary is a lot more difficult than acquiring social language. Academic language for ELLs is often referred by Cummings (1994) as cognitive academic language proficiency (CALP), whereas social language is called basic interpersonal communication skills (BICS) (Watts-Taffe & Truscott, 2000). BICS can take up to two years for ELLs to become proficient, and CALP can take from five to seven years. "Unlike social language, academic language is often context-reduced in that gestures, body language, and facial expressions that could facilitate the communication process are absent or diminished" (Watts-Taffe & Truscott, 2000, p. 259). Academic language is often introduced and taught within a brief period of time in the classroom, with hardly enough time for an ELLs to process, practice and internalize the new vocabulary. One way to make academic vocabulary content-rich is to scaffold instruction.
Scaffolds are designed to help support student language through careful planning of content delivery. "Such planning includes what students are to learn, how they will go about learning it, and ways to make the process successful" (Watts-Taffe & Truscott, 2000, p. 261). Scaffolding can be used in cooperative learning environments, and may include specifically designed graphic organizers, focusing on students' strengths. Another way to scaffold student vocabulary learning is to build background knowledge. All students, whether ELLs or English Only (EO), come to the classroom with background knowledge. "ESL students have background knowledge related to three areas: content (topic schema), language (linguistic schema) and text structure and organization (text schema) (Watts-Taffe & Truscott, 2000, p.261). Teachers can activate prior knowledge through pre-reading activities. By integrating new content into existing students' conceptual frameworks, vocabulary is committed to long-term memory and more transferable to new contexts (Watts-Taffe & Truscott, 2000).
Another area of vocabulary development for ELLs that is effective is in the transfer of cognates. Cognates are "vocabulary items in two different languages that are similar both orthographically and semantically" (August et al, 2005, p. 52). There are a number of Spanish and English cognates that can aid ELLs in vocabulary and language proficiency. Cognates can account from a third to a half of the average educated person's active vocabulary, or about 10,000 to 15,000 words (August et al, 2005). Students that are taught to use cognates as a reading strategy are more successful in inferring the meaning of unknown vocabulary. "Connections between pairs that are more phonologically transparent were more easily perceived than the connections between pairs that are opaque on the basis of sound" (August et al, 2005, p. 52). Even students that are not literate in their L-1 can hear cognates orally, and then identify them in L-2 language and texts. Studies have found that cognate recognition is developmental, with students' ability to utilize cognates increasing with age (August et al, 2005). Cognate recognition also helps increase the depth of ELLs vocabulary acquisition. There is some transfer between Spanish and English semantics, orthography, phonology and morphology. There are some Spanish and English suffixes that can help with vocabulary transfer.
Beck and colleagues have labeled vocabulary as either Tier I, Tier II or Tier III words (August et al, 2005). Tier I words are basic words that rarely require instruction for EO students, however ELLs will require instruction to lean these vocabulary words. Teachers can provide direct translation, use pictures or realia to aid Tier I vocabulary acquisition (August et al, 2005). Understanding that some Tier I words are polysemous is also important to keep in mind when providing vocabulary instruction for ELLs. False cognates also needed to be pointed out by the teacher to avoid confusion. Tier II and Tier III vocabulary words are academic or content specific in nature, and are encountered less frequently in everyday conversation, therefore they need to be explicitly taught, modeled and practiced with ELLs. Teacher and class read-alouds can help ELLs review and practice Tier II and Tier III vocabulary (August et al, 2005). "Because of the large gap in vocabulary development between ELLs and EO students and the limited time available for teacher-directed instruction, student-reinforcement activities were an important part if the intervention work" (August et al, 2005, p. 55). One strategy that teachers can use to help ELLs Tier II and III vocabulary reinforcement is to provide translated tapes of vocabulary words or texts, and to provide meaningful student-centered activities that promote interaction of peers.
In a study conducted by Carlo et al (2004), found that "a challenging curriculum that focused on teaching academic words, awareness of polysemy, strategies for inferring word meaning from context, and tools for analyzing morphological and cross-linguistic aspects of word meaning did improve the performance of both ELL and EO fifth graders to equal degrees" (Carlo et al, 2004, p. 203). This included not only increasing the breadth of academic vocabulary words, but also depth of vocabulary uses. The study concluded that increasing vocabulary also increased reading comprehension (Carlo et al, 2004). It was also concluded that direct instruction of vocabulary was an effective intervention, as well as teaching strategies to infer meaning from unknown words. The study found that a curriculum that introduced twelve to fourteen words a week, rather than twenty to thirty words, provided an opportunity to teach about words than to just teach a lot of new words. This helped provide valuable context and the learning of strategies that lead to a deeper, more meaningful understanding, that leads to greater comprehension (Carlo et al, 2004).
Conclusion
It wasn't until the 1980's and 1990's that vocabulary development entered the forefront of English as a Second Language (ESL) education. Since that time many studies have been conducted to explore the relationship between vocabulary, comprehension and language proficiency. There seems to be a direct correlation between an ELLs breath of vocabulary and reading comprehension.
There are many strategies that teachers can use to effectively teach Tier I, or high frequency words, as well as Tier II and Tier III academic or content specific, and less frequently heard words. Strategies should take into account the different components of linguistics, such as semantics, morphemes, and phonology. An understanding of transferable cognates can be an invaluable tool to help ELLs infer meaning from unknown vocabulary that they encounter in different contexts. False cognates should also be pointed out, as they may adversely affect comprehension. Teachers should be sure that they spend time planning effective lessons that scaffold new material, and take into account ELLs prior knowledge. By building upon existing schema new material is made more accessible, and is committed to long-term memory.
Incidental teaching of vocabulary is another way ELLs may acquire new vocabulary, but they have to be exposed to it repeatedly before it becomes a part of their vocabulary repertoire. Students need to have a middle to advanced level of proficiency to get the most use out of incidental teaching, whereas all students, both ELLs and EO students, can gain new knowledge through the explicit instruction of vocabulary.
