Did you know in English we have these great things called Suffixes?!
We use them to change words from
Noun ➡️ Verb ➡️ Adjective ➡️ Adverbs
Noun = Danger +suffix (ous) Adjective = Dangerous
Verb = Hope +Suffix (ful) Adjective = Hopeful or Hopeless
Unfortunately there are no real rules!
Learning common Suffixes can be a great way to improve your vocabulary!