naive
adjective(na-ive)
marked by or showing unaffected simplicity and lack of guile or worldly experience
Examples:
A teenager's naive ignorance of life. 
The naive assumption that things can only get better. 
This naive simple creature with wide friendly eyes so eager to believe appearances. 
naive
adjective(na-ive)
lacking information or instruction
naive
adjective(na-ive)
of or created by one without formal training; simple or naive in style
naive
adjective(na-ive)
not initiated; deficient in relevant experience
Examples:
He took part in the experiment as a naive subject. 
naive
adjective(na-ive)
inexperienced