After studying copula verbs
です in japanese grammar books by myself a couple of months ago, I was under the impresion that
だ is omittable as it is implied by the context.
Moving on, I recently began reviewing
i-adj with a different book, and found out plain non-past form of
i-adj are conjugated without
だ while plain non-past
na-adj are conjugated with
Examples would be:
That being said, it
だ only used with
na-adj or can it be used with
i-adj and ommitted whenever the speakers wants to?