Tzaddik Instead of Kadosh
Why is a righteous person called a Tzaddik and not called Kadosh?
Why do we use the term Tzaddik (righteous) rather than Kadesh (holy)?
There were several Sages that are called Kadosh - 'The Ari, HaKadosh,' 'Ohr HaChayim HaKadosh.' Sephardim are the ones who seem to use the title "kadosh" for their greatest Sages, and Chassidim the term "tzaddik."
The term 'tzaddik' refers to someone who does what is right and just in his relationships, whether they be between the human being and Hashem or between the human being and other human beings - even other creatures.
The term 'kadosh' refers to someone who has sanctified and elevated all aspects of his being - all his physical and emotional drives - to the service of Hashem. It refers to a very high level of service to Hashem.
The term tzaddik, however, is a more basic term that covers both the relationship with Hashem and the relationship with others.
A 'righteous person' (tzaddik) is also referred to as "lamed-vavnik" - "He's a real lamed-vavnik"...forming the number 36 by combining the two Hebrew letters 'lamed' (30) and 'vav' (6).
The Talmud records that the world is sustained on the presence of at least 36 tzaddikim (Sanhedrin 97b; Sukkah 45b). These hidden tzaddikim do their good deeds quietly. Their neighbors do not know who they are. If, however, that minimum of truly saintly people does not exist, then the world itself will perish.