The alphabet file determines how dtSearch counts words, so it is important that the same alphabet file used to index or search a file also be used to highlight hits. For more information on how hit highlighting works, see:
To ensure that the same alphabet used to index a file is used to highlight hits in that file, set the alphabetLocation to the folder where the index is located. The alphabet definition will be stored in this folder (in a file named INDEX_A.IX). If no alphabetLocation is specified, dtSearch will use the default alphabet.