The dictionaries used to spell-check the document are used to generate alternatives when a word is not found in the dictionaries. When searching for alternatives 4Spell takes into account which characters are similar. If, e.g., you have written a word that starts with "a" but which is not in the dictionaries, all words that start with an "à" are also searched for alternatives. Often these similar characters are the accented characters, but this needn't be the case. These similar characters are language dependent. For the Dutch language the file NL_SIMILAR.4SPELL is used (filename syntax is: "language"_SIMILAR.4SPELL). This file could look like this:
aà oóòöô eéèëê iïî uü ck
Note that in this list the characters "c" and "k" are listed as similar characters. In Dutch there is often confusion about these characters, and this is how you make 4Spell aware of this.