Learning English is not an easy task. One of the problems is that English has a very rich vocabulary, meaning students have many words to learn. On top of this, there are several ways to teach vocabulary, and students may find some methods better for them than others. One thing is for sure: it's always a good idea to teach vocabulary in context. Putting the words in a phrase or sentence helps students so much more than just giving them the words and definition alone. Try to use the new words in speech as much as possible when you are teaching them, to model how to use them. Repetition is key to remembering the words over long periods of time, so it's essential that your students practice a lot.