by by /ˈbaɪ/

adverb

1. () So as to pass a given point  ( by , past )
   so as to pass a given point
    Every hour a train goes past
   every hour a train goes past
   
2. In reserve; not for immediate use  ( aside , away , by )
   in reserve; not for immediate use
    Started setting aside money to buy a car
   started setting aside money to buy a car
    Put something by for her old age
   put something by for her old age
    Has a nest egg tucked away for a rainy day
   has a nest egg tucked away for a rainy day
   

preposition

1. () Close to; in the proximity of.  ( by , near )
   Close to; in the proximity of.
   
2. () By means of; with the assistance of; through the act or agency of  ( through , by )
   by means of; with the assistance of; through the act or agency of
   
3. () Indicating measurements or dimensions of an object.  ( by )
   Indicating measurements or dimensions of an object.
   
4. () Before a specific time or deadline.  ( by )
   Before a specific time or deadline.
   
5. () Progressing on or through a specific path or direction.  ( along , by )
   Progressing on or through a specific path or direction.