Definition

The Oxford Dictionary defines the word "maturity" as "deliberateness of action, mature consideration, due deliberation, fullness or perfection of natural development, ripeness, due promptness, the state of being complete, perfect, ready," and so on. This is the literary definition.
Physical Growth vs Mental Growth

However, in a general sense, maturity means complete physical and mental growth, or the state of adulthood. We all know or at least can make an intelligent guess of what complete physical growth means. It is easy to understand because physical growth is visible, measurable and does not continue beyond a particular age except in certain other ways. Almost every normal individual attains physical maturity in expected time. Only and rarely a few unfortunate individuals fail to grow normally because of some exceptional conditions or circumstances.

In case of mental maturity the trend is not the same. An individual can grow mentally for long. It is difficult to say when an individual actually stops growing mentally and whether he stops growing mentally at all till the end. Secondly, mental growth varies from individual to individual. Some people develop greater mental maturity and rationality much earlier in their lives compared to others. Thirdly, the same individual may exhibit varying degrees of maturity on different occasions, prompted by many facilitating and inhibiting factors, which are far too complex to be ascertained or explained with certainty.

However guarded an individual is and however mature he is mentally, at times he is bound to yield under pressure and show signs of immaturity. A vast majority of us are prone to this weakness. From time to time we take wrong decisions or display inappropriate behavior. This is very much human and there is nothing abnormal about it. In a way it is also helpful, especially when we let out our emotions, because it provides an outlet to our pent up emotions and helps us keep our inner balance.

Each of us have a child inside us. This child part in each of us is a product of our early experiences as growing infants. It is not unwanted. It in fact needs as much care as you needed it years ago as a child. What is undesirable, however, is to refuse to grow mentally along with age and acknowledge the reality of the present moment.

Quantifying the mental growth is therefore a real problem. It is difficult to say when and at what stage a person attains complete mental growth. By subjecting an individual to certain tests and testing situations, we may arrive at certain conclusions, but we cannot be sure how accurate such conclusions are.
What is maturity?

Maturity need not necessarily come with age, but with awareness and understanding, borne out of individual perception and cognitive experience. In an individual, it develops to the extent he organizes his consciousness on the basis of his empirical experience and verification of facts and to the extent he is free from his irrational thoughts, beliefs, prejudices, notions and emotions.

To be mature does not necessarily mean just a fully grown up individual. It is a combination of many things that includes age, awareness, intelligence, decision making ability and more. To be mature means:

1. to be realistic, to be in touch with reality and to be guided by facts,
2. to be responsible to self and others and to accept responsibility for self preservation,
3. to be willing to examine ones beliefs, fallacies, prejudices and assumptive behavior in an objective way and let them go,
4. to be guided by reason rather than emotions, to be able to distinguish the two and also at the same time accommodate them appropriately and intelligently in one's life and priorities,
5. to be assertive without being aggressive, to be friendly without the need to get attention, to disagree without the need to compete and to seek without the fear of failure or rejection,
6. to be flexible and open-minded rather than rigid and judgmental, to be amenable to new situations and receptive to new knowledge, to be willing to learn new skills and new responses,
7. to be inquisitive and exploratory, seeking answers to questions one does not know, gathering information before arriving at conclusions, stretching the mind to explore hidden possibilities and hidden potentialities,
8. to act spontaneously to an occasion or situation, free from preconceived notions, the compulsion to be perfect or correct, habitual or mechanical reactions
9. to be in touch with the present and enjoy the passing moment
10. To know what is possible and achievable and to acknowledge that which is not.

Who is a mature person?

Here is a brief description of what a mature person is. A mature person:

1. is concerned with facts,
2. goes by his experience rather than beliefs,
3. relies upon his reason rather than his emotions,
4. relies mostly upon his thinking,
5. uses his resources wisely according to the realistic needs and demands of the situation
6. weighs a situation carefully before drawing conclusions
7. Lives in the present
8. is open-minded, willing to learn and explore other possibilities, view points and alternatives
9. knows his limitations
10. is flexible
11. is spontaneous
12. has a healthy self image and sense of self
13. takes practical decisions based upon his perception of the situation
14. knows how to deal with his anxiety, fear and worries.

Maturity is accepting what is, willing to change what can be and knowing what cannot be. Maturity is to enter into a covenant with yourself, agreeing to be guided by reason, to be aware of your emotions, to strive for that freedom that is not of the prisoners of their own worlds.