This study investigates word difficulty and learning among learners of English as a foreign language (EFL) in Saudi Arabia. Difficulty factors examined in the study include repetition of words in learners’ EFL textbooks, word length and parts of speech, and adds a further consideration which is underexplored in the literature; word translation equivalents in the learners’ first language (L1). A total of 156 native Arabic participants were given a vocabulary test in which they had to identify whether a word was known to them and then to supply the meaning of the word in their L1 or L2. The findings showed a large effect of repetition on word learnability, accounting for 60% of the variance, followed by translation equivalence, which explained some 23% of the variance. Conversely, word length and the parts of speech element provided non-significant contributions to the overall model of learning. Thus, the results indicate a durable effect of repetition and a modest influence of L1 translation equivalent on the L2 vocabulary learning, regardless of the number of syllables in a word or the part of speech element.