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For years I have used '=>' as a sign meaning 'should be changed to' and I have long since forgotten whether this is a personal idiosyncrasy or an actual existing usage.

e.g. "in the sentence above word 'jive' => 'jibe.'"

Is this familiar usage to anyone? Anyone else besides me, I mean.

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I use this sign as "result". –  user8568 May 23 '11 at 15:56
@RegDwight, hm, don't see => or ⇒ there. –  Unreason May 23 '11 at 16:08
More anecdotal tales: I wouldn't know that this symbol meant anything in particular without context. The full sentence "In the sentence above, jive => jibe" provides enough context for me to know what was meant. –  MrHen May 23 '11 at 16:47
@Unreason: precisely my point. –  RegDwigнt May 23 '11 at 17:10

4 Answers 4

In logic it is used for implication:

p implies q is denoted with p enter image description here q

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Even outside of mathematics, the only sense I've known this symbol to be used for is "implies". –  Orbling May 23 '11 at 17:50
And other fields of maths, and also science, whether the user is thinking about implication (semantically/syntactically) or just some loose idea of deduction. –  Nicholas Wilson May 23 '11 at 18:52

In a regular text, I'd simply take it to mean changes/changed into, just like any random arrow, without any sense of desirability. Your particular interpretation is unfamiliar to me, and I believe it is not generally so used. Practice may be different in specific fields.

Of course you could indicate a desirable change with it, but I don't believe this desirability is inherent in the symbol.

As Unreason says, it means implication in formal logic: p => q means "if p, then q", just as p <=> q means "if p, then q; and if q, then p".

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Are you sure it is not → [->] rather than ⇒ [=>]? The first one usually mean to substitute in place of the other.

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Arjang, the LaTeX formatting plug-in is very resource-intensive, and is only turned on for SE sites that need it. EL&U sometimes needs fancy characters, but not fancy formatting, and fancy characters can be achieved in many much simpler ways than LaTeX. –  Marthaª May 23 '11 at 20:19

The usage is familiar to me also, but I don't know accepted it is. I don't know the approved editorial marks for paper proofreading (proofreading marks, but I've used '=>' in electronic text to say what I think should be done.

Which is to say, it is a reasonable symbol to mean "should be changed to", but therer is no official support for it that I know of.

('=>' has a technical but unrelated meaning in mathematical logic for a very specific kind of implication)

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