As we all know very well, our time and energy are not inexhaustible. We must therefore use them very carefully, that is, we must economize on them.

How can we do it in vocabulary learning? Table 1 is a useful guide. If you come across a word you do not know and feel that it is unlikely that you will use it yourself, you place it in your reading vocabulary. Hence you do not waste your time and energy in memorizing all the details about it, except that you make sure that you recognize it in your future reading. If instead you want to place it in your writing vocabulary, you have to make a close study of it.