This document discusses several key factors that influence second language acquisition, including motivation, attitude, age, intelligence, aptitude, learning styles, and personality. Motivation is one of the most important factors, and can be either integrative, relating to interest in the language and its culture, or instrumental, relating to practical uses of the language. Other important influences include a learner's attitude towards the language and its community, their age and any critical periods for language learning, general and multiple types of intelligence, as well as their language learning aptitude, style, personality traits like inhibition, anxiety and empathy.