Are there rules of thumb for counter sound changes?


I'm wondering if there are consistent (or at least fairly reliable) rules for
how to read numbers next to irregular counters, i.e. counters where you can't
just put together the number and counter word in every situation. For example,
the counter さい, the first number is not いちさい but いっさい. This is as opposed to
counters like まい, where all you need to do to form the counter is add the
number (e.g. ろく) and the counter, e.g. ろくまい.




The changes you're talking about are actually pretty regular. There _are_ some
irregular ones (一人【ひとり】、二人【ふたり】、三階【さんがい】), but what you're looking for is
pretty straight-forward.

[Wikipedia](http://en.wikipedia.org/wiki/Japanese_counter_word#Euphonic_changes)
has a pretty good summary of the sound changes.




The changes you're talking about are actually pretty regular. There _are_ some
irregular ones (一人【ひとり】、二人【ふたり】、三階【さんがい】), but what you're looking for is
pretty straight-forward.

[Wikipedia](http://en.wikipedia.org/wiki/Japanese_counter_word#Euphonic_changes)
has a pretty good summary of the sound changes.

