Distinguish

Distinguish

a) Transitive verb

1. To perceive a difference in: mentally separate
 * The fic had become so badly written that it was impossible to distinguish canon characters from Mary Sues.

2. To mark as separate or different
 * The Sunflower Official could be distinguished from its garden variety fellows by its tendency to communicate telepathically. Oh, and the suit helped, too.

3. To give prominence or distinction to
 * ''The student had distinguished himself in the not-so-lost art of pyromancy in his home continuum, and was therefore assigned to DOGA upon recruitment.

b) Intransitive verb

1. To perceive a difference
 * After one too many bad crossovers, the agent grew so delusional that she could no longer distinguish friend from foe and started glomping her enemies.

(Definitions taken from the Merriam-Webster Online Dictionary. The full definition can be found here. PPC-specific examples written by DawnFire, with amusement.)