A false friend is a pair of words in different languages that look or sound similar, but differ significantly in meaning.
This section is outdated: The false-friends.xml is not used anymore to
decide whether a word is a false friend, but only to generate the error message.
See e.g. confusion_sets_l2_de.txt instead.
Take an example:
<rulegroup id="ABNEGATION">
<rule>
<pattern lang="en">
<token>abnegation</token>
</pattern>
<translation lang="pl">poświęcenie</translation>
</rule>
<rule>
<pattern lang="pl">
<token inflected="yes">abnegacja</token>
</pattern>
<translation lang="en">slovenliness</translation>
<translation lang="en">untidiness</translation>
</rule>
</rulegroup>
This rule specifies that whenever you have “abnegation” in an English text and “mother tongue” option set to Polish, a warning will appear that “abnegation” means “poświęcenie” in Polish.
If you, however, are dealing with a Polish text checked with the option “mother tongue” set to English, you will see a warning for every instance of Polish word “abnegacja”; it will tell you that actually in Polish, it means the same as English “slovenliness” or “untidiness”.