What does the suffix ist mean in the word optimist

The suffix ist in the word optimist means full

Explanation:

The suffix “-ist" identifies someone who practices or studies a certain doctrine or subject or who adheres, or attempts to adhere, to a set of beliefs or system of principles; examples include: biologist, atheist, pacifist, artist, linguist, strategist, or Buddhist.

The suffix is often used with verbs that end in “-ize" i.e. strategize -- strategist, idealize--idealist or with nouns ending in "-ism” i.e. Buddhism --Buddhist, optimism -- optimist, atheism -- atheist, or with nouns (usually academic concentrations) ending in “-ology" i.e. biology -- biologist, meteorology -- meteorologist.

can you be a bit more specific