In Japanese, the vast majority of
な-Adjectives are originally nouns, and differ from nouns only in that they have their own set of conjugation rules. The dictionary form of a
な-Adjective will always be followed by
だ. な is only attached when describing another noun.
As we can see from these examples,
だ or
です is required at the end of a sentence, but な will be required when using a
な-Adjective to describe a noun.
な-Adjectives are mostly words of foreign (Chinese/English) origin. This is why they have evolved to require unique conjugation rules.
As a learner, it can be very difficult to identify what a
な-Adjective is, compared to a regular noun. Nouns conjugate with
の, while
な-Adjectives conjugate with な. A very simple trick that Japanese children learn is using the adverb
とても. If
とても sounds natural with a word, then it is probably a
な-Adjective, if it sounds unnatural, then the word is likely to be a regular noun.
From this example, we can see that
とても can be used to help identify
な-Adjectives. Basically, this is due to adjectives being measurable ‘very big’, ‘very small’, while nouns are not measurable ‘very dog’, ‘very boat’.