Acquisition of vocabulary is essential for learners of English. Successful learners need to make decisions about what vocabulary to learn, what aspects of vocabulary knowledge to master and how to study the vocabulary effectively. Vocabulary includes not only single word items but also multiword items. Learners have to decide which items to concentrate learning on. Items which occur more frequently in English may be useful but learners also need to acquire items relevant to their personal interests and circumstances. Vocabulary knowledge is multi-dimensional including elements related to form, meaning and use. This knowledge may develop through stages of receptive and productive ability. There are many strategies that can be used to learn vocabulary effectively. Points to consider may be whether to learn vocabulary in context or in isolation, whether to learn vocabulary in semantic groups, and how to reinforce learning for effective acquisition.