Professor emeritus at the University of Southern California. Krashen is a linguist, an educational researcher, and an activist.

Krashen has contributed to the fields of Second Language Acquisition (SLA), Bilingual Education, and Reading.

He is credited with introducing various influential concepts and terms in the study of second language acquisition, including the Acquisition – Learning Hypothesis, the Input Hypothesis, the Monitor Theory, the Affective Filter, and…