When is 大【おお】 and when is 大【だい】?


There was already a discussion here, with examples

[Reading of prefix 大](https://japanese.stackexchange.com/q/92884/31150)

but what about for 大イベント?

I was hoping one could generalize that 大+katakana=【だい】, but at least one word
seems to contradict that theory:

オオアルマジロ 《大アルマジロ》 【おおアルマジロ】 (n) (uk) giant armadillo (Priodontes maximus)

So what about 大イベント?

Is it 【おおイベント】 or 【だいイベント】?

It appeared here

<https://www.yomiuri.co.jp/economy/20220103-OYT1T50112/>

in the sentence

人生【じんせい】の大イベントを諦【あきら】める――。

_Giving up on life's big events--that's what it's all about._




It is だいイベント.

My impression is that だい is more common in most cases, apart from
animals/insects etc., like you mention. You can think those おお derive from
[大型]{おおがた}.

Another possible hint is you can replace the word following 大 by something
else of the same category: [大災害]{だいさいがい}.

* * *

#I mean above simply as a sort of mnemonic, and not something linguistically
valid.




It is だいイベント.

My impression is that だい is more common in most cases, apart from
animals/insects etc., like you mention. You can think those おお derive from
[大型]{おおがた}.

Another possible hint is you can replace the word following 大 by something
else of the same category: [大災害]{だいさいがい}.

* * *

#I mean above simply as a sort of mnemonic, and not something linguistically
valid.

