[charleski]

Originally Posted by DaleDe

Forbidden access. However http://en.allexperts.com/e/l/li/liga...ypography).htm
agrees with the definition in wikipedia.

I can see the page too. Here's the relevant passage (you need to set your browser encoding to utf-8 frabjous):

Æ is a grapheme formed from the letters a and e. Originally a ligature representing a Latin diphthong, it has been promoted to the full status of a letter in the alphabets of many languages.
...
In English, usage of the ligature varies in different places. In modern typography, and where technological limitations prevent (such as in use of computers and typewriters), æ is often eschewed for the digraph ae. This is often considered incorrect

So there you are, if you trust whoever wrote that, it's actually a grapheme . Actually, since that section is just lifted from Wikipedia, the page's history shows that the definition as a grapheme was inserted by OwenBlacker, FWIW, so we're relying on the opinions of a software development manager with a degree in molecular biology.

I think the real distinction is that ligatures are set for purely stylistic reasons, to avoid ugly shapes caused by character collisions. Æ and œ, on the other hand, have a well-defined history as characters that are distinct from their constituent letters. They are both (in English anyway) well on the way to being discarded just as the Old English þ became th in the 14th century.