по

preposition

1. used to indicate movement over a surface or movement bound to certain limits (usually continuous or repeating in time), on, over, through, along

   “Вървя по улицата.”

2. introducing the object of a targeted action or for an action related to certain state, on, over, for

   “Потупах го по рамото.”

3. in conjunction with countable nouns for price or quantity, expressing quantity, expressing distribution, by

   “По евро за книга.”

4. expressing approximate time

   “По обед.”

particle

1. used as a prefix to form comparative for adjectives and adverbs, more

   “Корабите са по-бавни от самолетите.”

particle

1. used for nouns, verbs and other parts of speech to form a comparative, more

   “По́ я обичам!”

2. used before prepositions to form a comparative, more, further

   “Областта е по́ на север.”