étudiés

In a sentence

• Les sujets étudiés cette année incluent la biologie et la chimie.

  The subjects studied this year include biology and chemistry.

  In this sentence, 'étudiés' is used as a past participle modifying 'sujets' to describe the topics that have been examined or learned.

• Ils ont étudiés ensemble tous les soirs avant l'examen final.

  They studied together every night before the final exam.

  Here, 'étudiés' is again a past participle, but in this context, it is part of a verb tense construction (passé composé) used to express that the action of studying took place in the past.

• Ces concepts doivent être étudiés attentivement pour bien les comprendre.

  These concepts must be studied carefully to understand them well.

  In this usage, 'étudiés' forms part of a passive voice construction indicating that the action of studying should be done regarding the concepts.