A strategy, activity, or procedure for teaching or supporting learning. Some common teaching methods include: lecture or exposition, group discussion, case study, demonstration and practice, role play, simulation, debate, field trips, and learning through discovery. A teacher's choice of method will be informed by factors such as the nature of the subject and topic to be taught; the ability of the learners and their level of motivation; the time available; the need for inclusion and differentiation; the degree to which the learners need to be actively involved; and the teacher's own preferred teaching style. A number of different methods may be employed within one lesson to provide learners with changes of activity, or one method may take up the entire lesson, as in the case of a lecture. A skilled teacher will be spoken of as having ‘a repertoire of methods’, indicating a confident flexibility of approach.