Alumno vs. estudiante
Though 'alumno' and 'estudiante' both translate to 'student' or 'pupil' in English, their usage and connotations in the Spanish language can be slightly different. Both words are used to describe individuals who are learning or studying, however, the context and type of relationship they imply can vary.
Alumno
'Alumno' is commonly used to refer to someone who is enrolled in a school or a particular course/class. This term emphasizes the relationship between the student and their teacher or educational institution.
Soy alumno de la Universidad de Salamanca.
(I'm a student at the University of Salamanca.)
Los alumnos deben entregar los trabajos antes del viernes.
(The students must submit the assignments before Friday.)
El profesor felicitó al alumno por su excelente trabajo.
(The teacher congratulated the pupil for their excellent work.)
Estudiante
'Estudiante' simply refers to someone who is studying, without specifically highlighting any relationship between this individual and a teacher or school. It's more general, often being used to refer to someone who acquires knowledge beyond formal education environments.
Soy estudiante de psicología.
(I'm a psychology student.)
Hay muchos estudiantes en la biblioteca.
(There are many students in the library.)
Mi hermano es un estudiante autodidacta de la historia europea.
(My brother is a self-taught student of European history.)
Summary
While there is significant overlap, typically 'alumno' refers to someone enrolled in a structured educational context guided by teachers, while 'estudiante' has a broader application. Anyone learning or studying, whether through formal education or independently, can be an 'estudiante'.