blotch n : an irregularly shaped spot [syn: splodge, splotch] v : mark with spots or blotches of different color or shades of color as if stained [syn: mottle, streak]

Blotch \Blotch\, n. [Cf. OE. blacche in blacchepot blacking pot, akin to black, as bleach is akin to bleak. See Black, a., or cf. Blot a spot.]
1. A blot or spot, as of color or of ink; especially a large or irregular spot. Also Fig.; as, a moral blotch. Spots and blotches . . . some red, others yellow. --Harvey.
2. (Med.) A large pustule, or a coarse eruption. Foul scurf and blotches him defile. --Thomson.

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A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. Stains are caused by the chemical or physical interaction of two dissimilar materials. Stains are used intentionally in a variety of fields, including in research (biochemical staining), technology (metal staining), and art (wood staining, stained glass.)

There can be intentional stains (such as wood stains or paint), and accidental stains (like spilling ketchup on your shirt). While the types of stains are very different in application, they all form in the same basic ways:

The primary method of stain formation is surface stains, where the staining substance is spilled out onto the surface or material and is trapped in the fibers, pores, indentations or other capillary structure of that surface.

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