frontière

In a sentence

• La frontière entre la France et l'Espagne est marquée par les Pyrénées.

  The border between France and Spain is marked by the Pyrenees.

  The word 'frontière' is used here in its geographical sense, indicating a physical boundary dividing two territories.

• La question des frontières psychologiques est importante dans les relations interpersonnelles.

  The question of psychological boundaries is important in interpersonal relationships.

  In this sentence, 'frontières' is used metaphorically to represent personal limits or boundaries within human interactions.

• Le nouveau traité a permis de délimiter clairement les frontières économiques entre les deux pays.

  The new treaty allowed for clearly defining the economic frontiers between the two countries.

  Here, 'frontières' refers to conceptual divisions, in this case economic distinctions between two nations.