The term "development" is often used interchangeably with "growth" and "maturation", but these terms need to be carefully distinguished.

Growth generally refers to the quantitative additions or changes in the organic structure. For instance as we become older, the body size, height, weight, proportion of parts of our body change in measurable ways. Also, the vocabulary increases.

Development, on the other hand, is a broader term which often includes growth, but is used more to refer to functional and qualitative changes in cognitive ability, perceptual ability, personality and emotional development and so on.

Maturation is a term that refers to the natural unfolding of changes with increasing age, e.g. hormonal changes as the individual reaches puberty. An example of this can be seen in breast development which is influenced by release of estrogen when a girl reaches adolescence. Maturation refers to the changes which are primarily biological in nature and occur due to our genetic programme.

Our biological structure follows a predetermined course of changes with time. This can be seen in the development of teeth during childhood. Changes in body proportions with age provide an example of such predetermined universal trends. The size of the head is roughly half of the whole body at birth, but the proportion keeps decreasing until adulthood, when it is less than one-fourth of the whole body. Therefore, maturational changes in our body are primarily due to the ageing process rather than learning or other factors such as illness or injury.\

The changes in behavior also occur due to learning. Learning takes place as a result of a person’s interaction with the environment. Maturation provides the raw material and sets the stage for learning to occur. Taking the case of learning to read, the child needs to be biologically ready. The eyes need to develop proper focusing ability before a child can learn to read. Therefore, maturation and learning jointly bring about changes in a person’s behaviour.

Evolution is a term that refers to species-specific changes. Evolutionary changes happen very gradually and are passed on from one generation to the other so that the species is better equipped for survival. The evolution from apes to human beings took place over a period of about 14 million years. Changes that occur at the level of species are called phylogenetic and those that occur at the level of individual are called ontogenetic. The term evolution is also used to describe the incremental changes that take place in the course of development.