My class 12 chemistry textbook says that phenol molecule has three reactive sites or it's functionality is three. But I am confused whether it is so or not, because, what I know, phenol has three double bonds, it must have a functionality of six. Besides, it also has an -OH which is yet another reactive site, so in all making it seven. Please help so that I may have a clear understanding of how to judge functionality of a monomer molecule.
Phenol has $3$ double-bond-equivalent, but not $3$ localized double bonds:
Look at its resonance structure:
Therefore, to a electrophile, there are $3$ reaction sites, which are the ortho- and the para- positions.
A nuecleophile does not attack phenol.