Possible Duplicate:
Adequate hyphenation of words already containing a hyphen
Is there any way to define permissible hyphenations for hyphenated words?
For example, even if I have hyphenations defined for the words semi and computable, LaTex still fails to break the word semi-computable. And if I add to the preamble
\hyphenation{se-mi-com-p-ut-a-ble}
that will only add a rule for semicomputable, not semi-computable.
EDIT: commentor had the answer Adequate hyphenation of words already containing a hyphen
Basically, writing semi"=computable should do the trick .
