These words refer to wavering coruscations of light, whether reflected from a moving surface or emitted unsteadily by the source of light itself. Sparkling would seem to suggest the throwing off of sparks, but as now used it is almost exclusively restricted to uneven, bright flashes reflected from light-catching objects: sparkling diamonds. Glittering is close to sparkling in meaning; sparkling perhaps suggests intenser stabs of more fleeting light, while glittering might suggest a larger mass of reflecting material that can be seen over a longer period of time and that casts reflections not so dependent on an exact perspective: a sparkling drop of dew; the whole glittering , rain-washed garden. In more general uses, sparkling suggests exuberance or animation, while glittering may have negative connotations of gaudiness, cheapnee or evil: her sparkling smile; glittering trinkets; glittering generalities; the glittering avarice in his eyes.

Flashing , when used for sources of light, suggests most strongly regular on-and-off alternation of light and darkness: the flashing red of the level-crossing light. Used for reflected light, it does not suggest regularity so much as intensity; it may not even suggest wavering light at all: the flashing, sunlit windows. Like sparkling, flashing may suggest liveliness, but more often of an unpleasant nature: the flashing eyes of rage. Both twinkling and scintillating describe, most specifically, starlight that appears to waver because of the moving atmosphere through which we see it. Twinkling can seem coy outside its nursery-rhyme context, but may escape this in descriptive uses: the twinkling lights of the city far below. In an extended use it may describe a quick, short movement or series of movements: the twinkling feet of the tap dancer. Scintillating has overtones of brilliance and has been over-used in figurative contexts to suggest elegance and wit: scintillating conversation.

Flickering , glimmering and shimmering all suggest a subdued or dim wavering of light. Flickering relates mostly to sources rather than reflections of light, but suggests a more sporadic or irregular wavering than the earlier words: patches of clouds that let through only flickering sunlight. The word has been over-used to describe firelight: flickering logs in the fireplace. Shimmering , in contrast, stresses reflected light that undulates quickly in a soft or dazzling blur: shimmering water. Glimmering may apply either to sources or the reflections; more than either of its two companion words, it stresses fitfulness and dimness, suggesting a source fainter than for flickering and slower undulations than for shimmering : the last coals of the glimmering fire; traces of moonlight in the glimmering darkness of the room.