Janus, the Roman god regarded as the gatekeeper of heaven, is usually depicted with two faces, front and back, each face presenting opposite views.; i.e. a two-faced icon.  (oxforddictionaries.com)  Depending on the answer you want, you have to catch Janus on his best side.  The English language includes several “Janus” words; i.e., words that are spelled and spoken the same, but strangely have opposite meanings, sometimes referred to as “contronyms., or occasionally as “contranyms”   A contronym comprises a homonym (a word with the same spelling, but different meaning), which is also an antonym (a word with an opposite meaning.)  Got that?  

Whoa!, you may say.  How can that be?  Contronyms, however, are not as rare as one may first believe.  Lets look at a few, as defined in the Goggle dictionary:

— Sanction:  (1) a threatened penalty for disobeying a law; (2) official permission or approval for an action.

— Fast:  (1) to move at high speed; (2) secured not to move.

— Cleave: (1) to adhere firmly, stick together; (2) to separate, as by splitting a diamond.

— Peruse:  (1) to read quickly, skim; (2) to read carefully.

— Overlook:  (1) to watch; (2) fail to notice.

— Model:  (1) The original; (2) A copy.

— Left:  (1) departed; (2) left behind.

—  Enjoin: (1) to prohibit an act; (2) to enforce an action.

— Finish: (1) completed; (2) destroyed.

— Continue: (1) to keep doing an action; (2) to suspend an action.

— Handicap: An advantage to ensure equality; (2) a disadvantage that prevents equality.

My two favorite contronyms:  sanction and peruse, which may be the most frequently used and cause the most uncertainly.  In order to understand the correct meaning of these words, one must concentrate on the context of the spoken or written word, not the word itself.  More Janus words exist, but to “peruse” the ten above should provide a “fast” “overlook” with an uncertain “finish.”  I will “continue” further comment.