We need to define instructional materials in the sense in which we, are using them. We would say that instructional materials include any material which can be seen or heard and which contributes to the learning process. Other names for instrucshipsal materials are Audio-Visual aids, teaching aids, and educational media.
Types of Instructional Materials
Primary aids: These include the actual objects as plants, animals, and other man-made objects in their natural place or dwelling. Some examples are fish in a river pond, crops on a farm, monkeys in a game reserve, airplanes at the airport, ships in the harbor, the Akosombo Dam, and severarealeal objects used in teaching. Where they are inof their natural dwelling places, their effect is even better. The point to note however is that these aids built-best effect in teachimodelsis means that they have a better effect than any of the others. It is for, this reason that teachers are always advised to try to use real objects and real situations to teach. Field trips are one way of trying to use real object acts in teaching.
Secondary aids; Secondary aids are mainly models of real objects, built-in solid forms. Prepared models such as cubed and cuboids in mathematics, models of houses and airplanes, and the like are secondary aids. For those that deal with hearing, they include the actual sound of birds, animals, cars and the like reproduced on a tape recorder. In terms of their effect on learning, secondary aids are inferior to primary aids but are necessary in cases where it, is difficult to provide the primary aid. For instance, since you cannot bring a ship to the classroom, the next option should be a model of a ship.
Tertiary aids: These include all the man-made materials and equipment that are used to support teaching. Films, photographs, maps, charts, prepared drawings, chalkboard drawings, radio teaching, and the like. Tertiary aids are not natural. They are even less natural than secondary aids.