One word for things which are different for different people, or exclusive to the person to which they belong?

What is an English words which describes that something is different for different people, or in other words, it's kind of exclusive to the person they belong to.

For example I want to say that there is nothing like "the-best-sleeping-duration". Sleep requirements vary with people. Different people have different sleep requirements.

Likewise, I want to say that there is nothing like the best method to study. Different methods are best-suited for different people. It's kind of subjective.

Solution 1:

I would go with personal based on your example.

1 : of, relating to, or affecting a particular person

While subjective is a synonym for personal, it has a connotation that you can control it. I wouldn't say your requirement for sleep is something you can change as easily as your opinion on a matter. Antonyms for subjective include objective, unbiased, and unemotional. Antonyms for personal include common, public, and general.

Solution 2:

I think you may mean subjective.

subjective

/səbˈdʒɛktɪv/

adjective

1. based on or influenced by personal feelings, tastes, or opinions. "his views are highly subjective"

synonyms: personal, personalized, individual, internal, emotional, instinctive, intuitive, impressionistic;

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