The same word can be used in different ways in the English language and it is the usage or function that determines which part of speech the word denotes in a sentence.
Therefore the meaning of the word is clear only if you read it in context of the sentence. Few examples of the words are some, the, up.
1.Adjective- There has to be some way out of it.
2.Pronoun- Some say the house is certainly haunted.
3.Adverb- Some twenty thieves barged into the house.
1.Def.Article- The dog barks at strangers.
2.Adverb- The careful you are, the safer.
1.Adverb- Rates of diesel cars are up.
2.Preposition- He went up the building.
3.Noun- The couple had their ups and downs in life.