brouillard

In a sentence

• Le brouillard était si dense ce matin que l'on ne voyait presque rien.

  The fog was so dense this morning that one could hardly see anything.

  In this sentence, 'brouillard' refers to a weather condition where water droplets form a thick mist near the ground, obstructing visibility.

• Un brouillard mental peut rendre difficile la concentration lors d'une longue journée.

  A mental fog can make concentrating during a long day difficult.

  Here, 'brouillard' is used metaphorically to signify confusion or a lack of clarity in one's thoughts.

• Il faut activer les phares pour mieux voir dans le brouillard.

  You need to turn on the headlights to see better in the fog.

  In this context, 'brouillard' again refers to the atmospheric phenomenon of fog that reduces visibility and requires safety measures.