Is the word Tall a Predicate adjective or a predicate noun?

A predicate nominative or a predicate adjectiverestates a noun following a linking verb or the object of a verb, telling something about the noun. The Word 'tall' could be a predicate adjective or a predicate noun, depending on how it's used in a sentence. Examples:

Predicate nominative: The size I need is a tall. (the noun tall is renaming the noun size)

Predicate adjective: My brother is very tall. (the adjective tall is renaming the noun brother)