Language learning aptitude refers to the "prediction of how well, relative to other individuals, an individual can learn a foreign language in a given amount of time and under given conditions". Foreign language aptitude itself has been defined as a set of cognitive abilities which predicts L2 learning rate, or how fast learners can increase their proficiency in a second or foreign language, and L2 ultimate attainment, or how close learners will get to being able to communicate like a native in a second or foreign language, both in classroom and real-world situations. Understanding aptitude is crucial for a complete picture of the process of second language acquisition. Knowledge about language aptitude has profound impacts in the field of Applied Linguistics, particularly in Second Language Acquisition (SLA) theory and in the practice of teaching and learning languages.

As a concept with historical origins in education and psychology, its application in applied linguistics will constantly be influenced by the latest findings in those disciplines of study. Following a revolution in studies of human cognition over the last few decades and major contributions especially from the fields of cognitive psychology and cognitive neuroscience, our understanding of human cognitive abilities has increased significantly. In other words, contemporary discussions of foreign language aptitude in applied linguistics would be substantially insufficient if not for research advances in other fields.

As with many measures of aptitude, language learning aptitude is thought to be relatively stable once a person matures.