we should know that some words can take different parts of speech in depend of the meaning of this word in the sentence. here are some exemples...
- the word (only) can be an adverb, an adjectif or conjunction.
adverb
"there are only a limited number of tickets available
"genes that were discovered only last year"
adjective
"the only medal we had ever won"
conjunction
"he is still a young man, only he seems older because of his careworn expression"
the word (that) for exemple can be a pronoun, adverb or conjunction.
pronoun
"that's a good idea"
"that's his wife over there"
adverb
I wouldn't go that far"
conjunction
she said that she was satisfied"