<p>I've read a few instances in reading mathematics and computer science that use the equivalence symbol <strong><code>≡</code></strong>, (basically an '=' with three lines) and it always makes sense to me to read this as if it were equality.  What is the difference between these two concepts?</p>

In languages that I have seen that differentiate between equality and equivalence, equality usually means the type
and
value are the same while equivalence means that just the values are the same.  For example:
```
```
int i = 3;
double d = 3.0;
```
```
i and d would be have an equivalence relationship since they represent the same value but not equality since they have different types.  Other languages may have different ideas of equivalence (such as whether two variables represent the same object).