Illuminate, illumine, light, lighten, enlighten, illustrate are comparable when meaning to fill with light or to throw light upon.
Illuminate implies the use of a bright light or of something comparable to it in such a way that what is dark is made bright or what is complicated, obscure, or vague is made clear.
Illumine is chiefly literary or poetical for illuminate. Light, lighten, and enlighten carry a stronger implication of providing with light for clear seeing than of throwing a light upon.
Light is the most consistently literal of these terms, though it often carries a suggestion of brightening the way of one who otherwise might stumble or go astray.
Lighten, like light, basically implies a making brighter or a lessening of darkness, but it has more extended and poetic use.
Enlighten, which has almost wholly lost its basic meaning of to make physically light or bright, is common when filling with intellectual or spiritual light is implied.
Sometimes the term implies that one has been supplied with information necessary to the understanding of something and sometimes it implies sufficient education and experience to enable one to meet all needs and, especially in the adjective enlightened, to remove or overcome superstition, prejudice, or intolerance.
Illustrate (see also EXEMPLIFY ) is somewhat rare in a sense which approaches that of illuminate and in which it suggests the shedding of luster rather than of light, embellishment rather than elucidation, and distinct exhibition rather than a bringing into view.