Sensitive periods: Young children experience transient periods of sensibility and are intrinsically motivated and are urged to activity by specific sensitivities. The child in a sensitive period is believed to exhibit spontaneous concentration when engaged in an activity that matches a particular sensitivity. For example, children in a sensitive period for order will be drawn to activities that involve ordering. They will be observed choosing such activities, becoming deeply concentrated, sometimes repeating the activity over and over, without reward or encouragement. Young children are naturally drawn to aspects in the environment that meet their developmental needs.

Simple to complex: A principal used in the sequence of presentations in a Montessori classroom. Children are first introduced to a concept or idea in its simplest form. As they progress and become capable of making more complex connections, they are eventually able to handle information that is less isolated.

Vertical age grouping: One of the hallmarks of the Montessori method is that children of mixed ages work together in the same class. Age-groupings are based on developmental planes. Children from 3 to 6 years of age are together in the classroom. Because the work is individual, children progress at their own pace; there is cooperation rather than competition between the ages