冗談のつもり the grammatical explanation

Question

Since plain form words can attach to つもり, we can just attach the i-adjective 若い to it as is.

When our plain form word is a NOUN, we'll add a の after it. And for na-adjectives, we add a な after them. For example, later we'll see:

冗談{じょうだん}のつもり

in this grammar rule. We attach the つもり with the plain form (noun,adjective,verb). Is this つもり acting as a noun, because when its attached with an adjective, we place a な in between them, and with noun の.

Answer 1

You asked a very similar question several days ago. This つもり is another 形式名詞. If you really want a meaning as a noun, it would be something like "intention", "plan", "assumption" or "belief". But つもり is usually translated into English without using these nouns.