How to pluralise terms made up of more than one word

As you know, in English you generally make a word plural by adding an ‘s’ at the end. There seems to be some confusion, though, about how to make plurals of terms made up of more than one word. For example, do you say bicycles shops or bicycle shops? Do you say power of attorneys or powers of attorney?

The answers are bicycle shops and powers of attorney.

The rule is that you pluralise the “head” of the term.

The term bicycle shop is typical of most noun groups. The “head” is the last word in the group. The previous word or words act as an adjective. So the last word in the group is pluralised. Here are some more examples:

Bank account => Bank accounts
Company car => Company cars
Price limit => Price limits
Termination notice => Termination notices
Service charge payment => Service charge payments
Group redundancy procedure => Group redundancy procedures
Employee share option scheme => Employee share option schemes

However, a term like power of attorney acts rather differently. Power is the “head” and of attorney is an adjectival phrase which describes the “head”.

Here are some other examples of terms that behave in the same way:

Article of association => Articles of association
Attorney-in-fact => Attorneys-in-fact
Attorney general => Attorneys general
Code of conduct => Codes of conduct
Condition precedent => Conditions precedent
Conflict of interest => Conflicts of interest
Course of action => Courses of action
Court of Appeal => Courts of Appeal
Court of first instance => Courts of first instance
Daughter-in-law => Daughters-in-law
Head of State => Heads of State
Notary public => Notaries public
Statement of claim => Statements of claim

plural of attorney at law, plural of attorney general, plural of attorney in fact
Source: http://docphy.com/business-industry/personal-finance/insurance/pluralise-terms-made-one-word.html