Age - Homework

Mature 

Mature means you are fully developed physically and mentally. You may been seen as a adult or 'grown up'.

Words to describe 'maturity' are:
Sensible
Aware
Knowing
Together
Intelligent
Wise
Complete
Grown-up
Developed
Prepared
Sophisticated
Old
Trustworthy
Polite
Boring
Organised
Experienced
Adult
Formal
Up-tight

Immature 

Immature means that you are not fully grown or developed. Some see immaturity as a lack of wisdom, and associate this with youths. 

Words that describe 'immaturity' are:
Playful
Out of control
Juvenile
Childish
Inexperienced
Kid
Youthful
Undeveloped
Unsophisticated
Young
Innocent
Childlike
Naive
Simple
Spontaneous
Laid-back
Noisy
Annoying
Out of control
Enthusiastic
Submissive
Vulnerable