most cost-efficient
"economical" has no comparative or superlative form. You would say "more economical" or "most economical."
The noun form of the adjective 'expensive' is expensiveness.The word 'expensive' is the adjective form of the noun expense.
The noun form of the adjective 'needy' is neediness.The word 'needy' is the adjective form of the noun need.
Expensive is an adjective. That house is expensive.
The word prosperously is the adverb form of the adjective prosperous.The noun form of the adjective prosperous is prosperousness.A related noun form is prosperity.
The superlative form of an adjective indicates the highest degree of the quality that the adjective describes. The superlative form of oily is oiliest.
the superlative form of sad is SADDEST
Longest is the superlative.
In is not an adjective, so it doesn't have a superlative form
Get is not an adjective so it doesn't have a superlative form
Yes. it is the superlative form of the adjective bad. It can also be the superlative form of the adverb badly (most badly).
The comparative form for the adjective 'wide' is wider.The superlative form for the adjective 'wide' is widest.
bad is an adjective worse is the comparative form of bad - comparative adjective worst is the superlative form of bad - superlative adjective
Yes, it is an adjective. It is the superlative form of the adjective "weak."
Either is not an adjective. It has no degrees.
The comparative form for the adjective 'proud' is prouder.The superlative form is proudest.
No, it is an adjective. It is the superlative form of the adjective "thick."