The おお reading is out of the scope of this question - it might be involved in the answer though
I'm learning some vocabulary, and noticed that 大 was sometimes read だい, sometimes たい.
The instance that surprises me the most is these two words:
What is the reason why 大 is read たい in the first word, and だい in the second? I would have expected it to be read the same in these two words, since they must come from the same construct or be derived from the same rule.
Is there any rule that states when 大 should be read たい, and when it should be read だい?