Exceptions
If the i and the j belong to different syllables, such as in the mathematical term bijectie (syllablized "bi•jec•tie"), they are not considered to form a ligature or a single letter. Earlier statements about sorting ij on par with y, keeping ij together in wide inter-letter spacing, the single square in crossword puzzles, etc., do not apply.
In some other languages, the combination i+j can exist as well, but in those foreign (from Dutch point of view) words, that combination should not be considered to be a single letter either. In the Netherlands, this letter combination is sometimes confused with the letter y. In several Dutch shops, byoux or byous are for sale according to the signs, instead of bijoux (jewels).
Read more about this topic: IJ (digraph)