i-Adjective before a Noun, here with a "な"

Question

Source: Lecture notes: Japanese grammar, basic course, University of Duisburg, Germany, Ch. 13, page 5 https://www.japanisch-grund-und-intensivkurs.de/grammar/sem1/lesson13/erweiterung_der_partikelfunktionen

Sentence under question:

大きな鳥{とり}が空{そら}を飛んでいます。

My question: "ookii" is an i-adjective, followed by a noun "tori". Why does the i-adj. in this sentence have a "na"?

What I found in "Tanoshii Japanese dictionary": "大{おお}きな noun or verb acting prenominally". Sorry, but at my present Japanese level I really can't grasp this explanation.

Could anyone please answer my question and maybe give me a good source with explanation? Thanks

Answer 1

大きい is an i-adjective. 大きな behaves like a na-adjective when used before a noun.

We can write both 大きな犬 and 大きい犬. They are both grammatically correct and natural. This is the situation in which the adjective is used 'prenominally', i.e. before a noun. But, as you probably know, in Japanese adjectives can also be used as predicates, e.g. 犬が大きい.

For na-adjectives the na is normally dropped when being used as a predicate, e.g. 犬がきれい. So you might expect that you could also write 犬が大き, but this would be ungrammatical. 大きな and 小さな (I'm sure there are others) are special cases where you cannot use them as a predicate.

In the pre-nominal form 大きい and 大きな are pretty much interchangeable, but see this link (and the duplicate link) for a deeper discussion.