Key words definitions and their weight factors are stored in file : /etc/MailScanner/spam.assassin.prefs.conf
The point is that such definitions MUST be given in a certan way, or they will simply not be applied.
Here is how those definitions must look :
header mart14 Subject =~ /discount/i
describe mart14 The Subject: containes discount
score mart14 15.0
header mart15 Subject =~ /satisfaction guaranteed/i
describe mart15 The Subject: containes satisfaction guaranteed
score mart15 15.0
And here is a thing that MUST not be done, or the definition will not work : definition name (in the above example that is “mart14 and mart15) MUST NOT have in it nothing except alphanumerics (so not such things as -, ., _ etc).