Adjective

(en adjective)

Having, or expressing doubt; questioning.

* {{quote-magazine, year=2012, month=March-April

, author=Colin Allen , title=Do I See What You See? , volume=100, issue=2, page=168 , magazine=(American Scientist) citation , passage=Numerous experimental tests and other observations have been offered in favor of animal mind reading, and although many scientists are skeptical , others assert that humans are not the only species capable of representing what others do and don’t perceive and know.}}

My teacher was skeptical when I told her my dog ate my homework.

I can see why people are so skeptical [sic] about him, but I think he's on to something here. (regarded by organizations such as the BBC as an error)

Of or relating to skepticism or the skeptics.

Adjective

(en adjective)

Expecting the best in all possible ways.

in an optimistic mood

optimistic plans

took an optimistic view