Vocabulary learning is the process acquiring building blocks in second language acquisition Restrepo Ramos (2015).
The impact of vocabulary on proficiency in second language performance "has become […] an object of considerable interest among researchers, teachers, and materials developers" (Huckin & Coady, 1999, p. 182).
From being a "neglected aspect of language learning" (Meara, 1980, as cited in Xu & Hsu, 2017) vocabulary gained recognition in the literature and reclaimed its position in teaching.
Educators shifted their attention from accuracy to fluency by moving from the Grammar translation method to communicative approaches to teaching.
It is important to treat these types as complementary -rather than mutually exclusive- by using different vocabulary learning strategies and their combinations.
Dodigovic (2013) and Nation (2006) emphasize the same distinction - only using a different term for the one side of this dichotomy: deliberate vocabulary learning.
Elgort (2011) uses the term deliberate, while DeCarrico (2001) prefers to talk about "explicit versus implicit learning" (p. 10).
Whatever terminology is used in the literature by different authors, the two major types of vocabulary learning are discussed: explicit and incidental.
Building on this classification, Xu and Hsu (2017) suggest two major categories of vocabulary learning strategies – direct and indirect.
Before moving on to presenting the literature, it is important to mention that when talking about deliberate vocabulary learning, various terminologies are used by different linguists and writers.
However, they also believe that in order to be able to build up sufficient vocabulary and acquire the necessary strategies to handle the context when reading, learners need support.
Ma and Kelly (2006) argue that learning a word requires more “deliberate mental effort” than merely being engaged in meaning-focused activities.
Restrepo Ramos (2015) indicates that “there is strong evidence that supports the occurrence of incidental vocabulary learning through reading for meaning comprehension” (p. 164).
Huckin & Coady (1999),[2] on the other hand, argue that "extensive reading for meaning does not automatically lead to the acquisition of vocabulary.
Thus, to develop incidental vocabulary learning, the learners should be exposed to the words in different informative contexts, following the bottom-up processing of the readings.