More on Collective nouns

There are, further, so called collective nouns, which are singular when we think of them as groups and plural when we think of the individuals acting within the whole (which happens sometimes, but not often).

audience band class committee crowd dozen

family flock group heap herd jury

kind lot [the] number public staff team

Thus, if we're talking about eggs, we could say "A dozen is probably not enough." But if we're talking partying with our friends, we could say, "A dozen are coming over this afternoon." The jury delivers its verdict. [But] The jury came in and took theirseats. We could say the Tokyo String Quartet is one of the best string ensembles in the world, but we could say the Beatles were some of the most famous singers in history. Generally, band names and musical groups take singular or plural verbs depending on the form of their names: "The Mamas and the Papas were one of the best groups of the 70s" and "Metallica is my favorite band."

Note that "the number" is a singular collective noun. "The number of applicants is steadily increasing." "A number," on the other hand, is a plural form: "There are several students in the lobby. A number are here to see the president."

Collective nouns are count nouns which means they, themselves, can be pluralized: a university has several athletic teams and classes. And the immigrant families kept watch over their herds and flocks.

The word following the phrase one of the (as an object of the preposition of) will always be plural.

• One of the reasons we do this is that it rains a lot in spring.
• One of the students in this room is responsible.

Notice, though, that the verb ("is") agrees with one, which is singular, and not with the object of the preposition, which is always plural.

When a family name (a proper noun) is pluralized, we almost always simply add an "s." So we go to visit the Smiths, the Kennedys, the Grays, etc.When a family name ends in s, x, ch, sh, or z, however, we form the plural by added -es, as in the Marches, the Joneses, the Maddoxes, the Bushes, the Rodriguezes. Do not form a family name plural by using an apostrophe; that device is reserved for creating possessive forms.

When a proper noun ends in an "s" with a hard "z" sound, we don't add any ending to form the plural: "The Chambers are coming to dinner" (not the Chamberses); "The Hodges used to live here" (not the Hodgeses). There are exceptions even to this: we say "The Joneses are coming over," and we'd probably write "The Stevenses are coming, too." A modest proposal: women whose last names end in "s" (pronounced "z") should marry and take the names of men whose last names do not end with that sound, and eventually this problem will disappear.

The names of companies and other organizations are usually regarded as singular, regardless of their ending: "General Motors has announced its fall lineup of new vehicles." Try to avoid the inconsistency that is almost inevitable when you think of corporate entities as a group of individuals: "General Motors has announced their fall lineup of new vehicles." But note that some inconsistency is acceptable in all but the most formal writing: "Ford has announced its breakup with Firestone Tires. Their cars will no longer use tires built by Firestone." Some writers will use a plural verb when a plural construction such as "Associates" is part of the company's title or when the title consists of a series of names: "Upton, Vernon, and Gridley are moving to new law offices next week" or "Shadrach, Meshach, Abednego & Associates have won all their cases this year." Singular verbs and pronouns would be correct in those sentences, also.

The names of sports teams, on the other hand, are treated as plurals, regardless of the form of that name. We would write that "The Yankees have signed a new third baseman" and "The Yankees are a great organization" (even if we're Red Sox fans) and that "For two years in a row, the Utah Jazz have attempted to draft a big man." When we refer to a team by the city in which it resides, however, we use the singular, as in "Dallas has attempted to secure the services of two assistant coaches that Green Bayhopes to keep." (This is decidedly not a British practice. In the UK, the city or country names by which British newspapers refer to soccer teams, for example, are used as plurals — a practice that seems odd and inconsistent to American ears: "A minute's silence will precede the game at Le Stadium today, when Toulouse play Munster, and tomorrow at Lansdowne Road, when Leinster attempt to reach their first European final by beating Perpignan" [report in the online London Times].)

Source: http://grammar.ccc.commnet.edu/GRAMMAR/plurals.htm#problems