A discussion of the ease or difficulty of learning vocabulary words in a second language looks at a variety of issues in second language instruction. Research on factors in vocabulary learning is discussed, focusing on such factors as similarity in form and morphology, deceptive morphological structure, different syntactic patterning in the native language, differences in the classification of experience in the first and second languages, abstractness, specificity, negative value, connotations nonexistent in the native language, differences in the pragmatic meaning of near-synonyms and first-language translation equivalents, the learning burden of synonyms, and the apparent rulelessness of collocations. It is argued that word learnability (i.e., the ease or difficulty of learning a particular word) can serve as a guideline to the teacher in: (1) the selection and presentation (quantity, grouping, language of presentation, isolation or context) of words to be taught; (2) facilitation of long-term memorization (through meaningful tasks, mnemonic techniques, rote learning, and reactivation); (3) development of self-learning strategies, and (4) assessment of vocabulary knowledge. (Author/MSE)