"elderly"係名詞定形容詞黎架~

Please kindly note the below usage of English:

The + adjective = people with that property

The phrase "the elderly" means people who are old. As a result, the first sentence (Who will take care of the elderly) is correct.

In the second sentence, elderly is an adjective for describing 'my father'.

For the question of the part of speech, elderly is an adjective. I have checked the yahoo dictionary and adjective was indicated clearly. Please double check.

Take care of the elderly (people). is like Take care of the sick(people)- elderly is an adjective like sick. - http://dictionary.reference.com/browse/elderly
Take care of the elders.- elder is the noun. -http://dictionary.reference.com/browse/elder?s=t

2012-04-08 06:43:04 補充：
When an adjective is preceded by 'the' as in "the elderly", the adjective functions as a noun. Other examples are, the rich and the poor, "The good, the bad and the ugly".

2012-04-08 11:59:48 補充：
Yes, it applies to any adjective including 'horrible'. See example here -http://insidemovies.ew.com/2011/12/01/sundance-midnight-movies-the-gross-the-vile-and-the-hilarious/