Diagnosis
These ideas work even in more subtle cases. A boy brings an insect in a box to a natural history museum. He asks an expert "What is this?" The expert says "You mean, apart from it being a beetle?" When the boy nods, the expert looks at the insect under a magnifying glass, or a binocular microscope. Chances are, it is a common beetle, and the expert can give the boy quite a lot of information about it.