In theories of personality, personality trait consists among others and type. Trait itself explained as a theoretical construct that describes the unit basic of personality. Trait described the consistency of the response from individuals in different situations. While type is a grouping of the various trait. Compared with the concept of trait, type has a level of regularity and greater generality than the trait.

Trait is a disposition to behave in certain ways, as reflected in the behavior of people in various situations. Trait theory is a  Personality theory that is based on several assumptions, so:

• Trait is a consistent pattern of thoughts, feelings, or actions that distinguish one person from another, so that:
• Relatively stable trait over time
• Trait consistent from situation to situation

Trait is the basic tendency that persist for life, but the characteristic behavior can be changed because:

• There is an adaptive process
• The different strengths
• The combination of an existing trait

Basic personality trait levels change from late adolescence to adulthood. McCrae and Costa believe that during the period from age 18 to 30 years, people are in the process of adopting a stable trait configuration, a configuration that remained stable after the age of 30 years (Feist, 2006).

Trait theory first raised by Gordon W. Allport. Allport addition, there are two other experts who developed this theory. They are Raymond B. Cattell and Hans J. Eysenck.

According to Allport, genetic and environmental factors are equally influential in determining human behavior. Not only his own heredity or environmental factors alone that determines how personality is formed, but through the reciprocal influence of genetic and environmental factors that gave rise to personality characteristics.
Regarding a genetic role in the formation of personality, there are 4 important insights to note:

• Although genetic factors play an important role towards the development of personality, non-genetic factors still have a role for variation personality

• Although genetic factors are important in influencing the environment, non-genetic factor is the factor most responsible environment will be a difference in people

• Experiences in the family is an important although the family environment is different for every child in relation to the type of child gender, birth order, or a unique event in the lives of families in each child.

• Although there is a strong genetic contribution to personality trait, does not mean that the trait is fixed or can not be influenced by the environment.

Sources:
Cooper, C.L., & Payne, R. (1991). Personality and stress: Individual differences in the stress process. England: John Wiley & Sons Ltd.
Feist, J. & Feist, G. J. (2006). Theories of personality. (Ed. Ke-6). New York: McGraw-Hill Inc.
Hjelle, L.A., & Ziegler, D.J. (1992). Personality theories. Singapore: McGraw Hill Book.
McCrae, R.R., & Allik, J. (2002). The Five Factor Model of personality across cultures. New York: Kluwer Academic/ Plenum Publishers.
Pervin, L. A. (1993). Personality: theory and research. (Ed. ke-6). Canada: John Wiley & Sons.
Pervin, L. A. (1996). The Science of personality. USA: John Wiley & Sons
Linzey & Hall. (1993). Theories of personality. (4th ed). New York: John Wiley & Sons.