This document summarizes several key factors that affect second language acquisition. It discusses individual factors like age, personality, motivation, experiences, cognition, and native language. External factors discussed include curriculum, instruction, culture and status, motivation, and access to native speakers. Affective factors that can influence language learning are self-esteem, inhibition, risk-taking, anxiety, and empathy. Younger children tend to acquire a second language more easily than older learners due to biological factors, but older children and adults learn more rapidly initially. Personality, motivation, experiences, and cognitive abilities also impact success in acquiring a new language.