I know that a functional group gives definitive property to an organic compund. But my text book claims carboxylic acid is a functional group but isnt carboxyl the functional group with a formula -COOH , is the text book wrong or am i missing something? And similarly isnt hydroxyl the functional group of alcohols rather than alcohol being the functional group. Could you please clear this out ?
Your books statement that "carboxylic acid is a functional group" doesn't seem quite right to me. I think it's better to say that a carboxylic acid is an organic molecule containing a carboxyl functional group.
Similarly, I wouldn't say that an alcohol is a functional group, but that an organic molecule containing a hydroxyl group is an alcohol.
Of course you can have single large molecules with multiple functional groups that could be called, at once, for example, an alcohol, a ketone and a carboxylic acid, because it contains a hydroxyl functionality, a carbonyl functionality and a carboxyl functionality.
I hope this addresses what you were asking, don't hesitate to ask if I missed something.
Carboxyl, hydroxy, chloro, amino etc are prefixes which represent the functional group used. They are standard 'PREFIXES', note that, and not the functional groups themselves. They represent the functional group in the compound while naming.