These words refer to a specific thing or piece of data summoned up to represent or verify a general type or thesis. Sample usually indicates something that is physically present for inspection as a representative of some larger entity.

• The interior decorator had brought along samples of the fabrics he had selected for the curtains and upholstery of the room; The enclosed essay is a sample of my writing.

Most concretely, illustration may indicate graphic material that accompanies a written text to supplement it or help explain it: a book on architecture with beautiful illustrations ; an algebra textbook with numerous illustrations . But the word can refer to any citing of specific material to supplement, explain or demonstrate a thesis or train of thought: He threw in two humorous anecdotes as illustrations of his main point. The word can refer also to something that is merely alluded to rather than actually presented: She cited the slaughtering of Albigensians and Incas in illustration of her argument that previous attempts at genocide were not uncommon.

Specimen stresses even more than sample the physical presence of a representatively individual. The word is also clinical in tone, suggesting a laboratory or scientific context: microscopes set up with specimens of the four blood types; rock specimens ; entomological display cases with specimens of many insect species. As in the last case, specimen can often imply that something is dead or has been killed, but this is not always so: cages to separate the healthy specimens from those that had contracted the disease. Beyond the scientific context, the word can apply to anything that seems representative of a type or larger whole: a perfect specimen of farcical fiction; checking the endorsement against other specimens of the man’s signature. When applied to a person, the word suggests someone noticeably typical, eccentric or physically impressive; in this use, an ironic tone may be present: a standard specimen of the conformist, middle-class liberal; odd specimens of underworld life; a girl who was quite a succulent specimen ; a real specimen of a man.

Example is the most general of these words. While it may indicate something physically present as a specimen , more often the word suggests the citing of supplementary material, comparable to the similar use of illustration . But example often implies brief citations given for clarity rather than to corroborate a thesis: a list of examples showing faulty and correct constructions in relation to each new grammatical rule. The implication that an example is an aid to learning or study comes to the fore when the context is that of discipline: a punishment was intended to make an example of him before the whole class.

Instance points to a concrete example or illustration of a general thesis, particularly one drawn from the past: asked to cite instances of oligarchic rule in European history. The word can refer also to an isolated or minor occurrence in the present: scattered instances of rioting even after the major flare-ups was over. Sometimes, the word can refer to exceptions rather than typical samples : a few instances of disagreement at the otherwise harmonious meeting. Or the word can apply to details that are part of an occurrence, even when no general thesis is being proven or defended: noting instances of the crowd’s behaviour as it heard the new. Case can function vaguely in place of other words here, but it may particularly refer to a greater body of material looked at in some detail: a presentation of cases in which an open conflict existed between the king and the papacy. By contrast, the word can refer to a whole argument rather than to its examples : his case for nuclear disarmament; the Crown’s case against the suspect. It can also refer to a specific medical or psychiatric instances : his analysis of some hundred terminal cancer cases . The word often suggests any significant or unusual body of details that is isolated for intensive study because of its puzzling or controversial nature: a strange murder case ; an investigation of alleged cases of levitation by Hindu gurus.