So I was looking for the "not-equals to" symbol in the UNICODE table, and I wound up looking at the other various mathematical operators, and some of them are just - weird.
The all-caps text after the characters are the UNICODE character name - every UNICODE character (all 16,000+ of them) have official names.
≦ - LESS-THAN OVER EQUAL TO - Not sure why you'd want this over ≤, but why not?
≧ - GREATER-THAN OVER EQUAL TO - the opposite, of course
≪ - MUCH LESS-THAN - there's a "much less-than" sign?
≫ - MUCH GREATER-THAN - well, of course
≰ - NEITHER LESS-THAN NOR EQUAL TO - and this differs from ">" how?
≱ - NEITHER GREATER-THAN NOR EQUAL TO
≶ - LESS-THAN OR GREATER-THAN - so, in other words, not equal, right?
≷ - GREATER-THAN OR LESS-THAN - OK, even assuming the one above was useful, WHY would anyone want to reverse them?
≸ - NEITHER LESS-THAN NOR GREATER-THAN - So that leaves what, equal to?
≹ - NEITHER GREATER-THAN NOR LESS-THAN - I guess for excessive completeness...
≔ - COLON EQUALS - yeah, I see the need for a special character for ":=".
≕ - EQUALS COLON - and, of course, gotta have one for "=:"
The next progression is fun:
≅ - Approximately equals, seen and used that plenty
≆ - Approximately equals but not actually equal to - haven't seen that, but, why not?
≇ - Neither approximately nor actually equal to
Slight correction
I don't know all of these symbols but the last three of them at least actually meas, when you compare two geometrical figures (same order as above):
So now you know.
Every char is sacred ...
"Much less than" is used in physics to describe negligible effects, for instance relativity is ignored when the speed is much less than the speed of light.
I admit the others seem rather pointless when you only consider ordered fields like real numbers. But the imaginary number i is neither less nor greater than -i, but they're not equal either. Some goes for vectors or even better: apples and oranges. :)
And mathematically speaking "greater-than" is defined as "neither less-than nor equal to". So, they're in fact the same, but "greater-than" is actually just colloquial speech.
Greater-than or Less-than
Hi!
Funny remarks. But I'm pretty sure these symbols for some very sophisticated reasons we bare humans do not understand.
On the ? sign, it might seem strange but it is not exactly what you think. I've seen it used to depict an inequality that can change sign depending on a condition. Of course, it assumes that the effect of the condition on the inequality can be understood in the context.
To make myself clearer, a trivial example :
?(x_i) ? ?(y_i) if ?i, x_i ? y_i
Which is simpler than writing
?(x_i) ? ?(y_i) if ?i, x_i ? y_i
and
?(x_i) ? ?(y_i) if ?i, x_i ? y_i
The answer to your questions
Some of the operators may seem mystifying, indeed, until you realize that operators can be unordered. What is the meaning of 10.0
You omitted
http://www.fileformat.info/info/unicode/char/22da/index.htm LESS-THAN EQUAL TO OR GREATER-THAN
And yea, as someone said already, they aren't mystic at all when you study relations that are not total orders. (Real numbers are totally ordered, vectors, apples, cardboard boxes aren't. You can have two boxes such that neither fits into the other so they can be said neither larger nor smaller nor equal...)