Hi again,
1. Animals have a tail.
2. Animals have tails.
I'd like to make a few more comments on this.
I completely agree with CJ's points. The ambiguities that are built into these few words, because of the nature of the English grammar involved, are extensive. I just didn't choose to focus on those. Instead, I wanted to consider the way we communicate about this kind of thing in everyday English.
I think that in many conversations, these ambiguities will have little importance and will pass undiscussed. In many other cases, they will be of considerable importance and clarification will be required. This clarification may consist either of a more careful choice of wording initially or of subsequent questions and explanations.
When we speak of something, both speaker and listener often bring some prior knowledge to the communication. For example, we all know that animals, at least most, have tails and that many animals do not share one tail. Thus, neither of the above sentences will cause serious miscommunication in these areas. Similarly, I would argue that many people, although not necessarily everyone, will enter the conversation with an awareness that most people who have a chequing account will have no more that one per person. Again, the likelihood of miscommunication is reduced.
However, let's consider a topic where people are less likely to have prior knowledge in common. In N. America, credit cards are widespread and many people have more than one per person. Let's assume that I want to say that most Canadians have one card, not zero and not more than one. I can say this in a number of ways, some of which are more precise and some less precise. Two common sentences I might use in everyday English are as follows.
1. Most Canadians have a credit card.
2. Most Canadians have credit cards
In my original reply, I didn't intend to suggest that there were not other more precise and less ambiguous ways to say this. The original point I was trying to make, and that I would still maintain, is that of these two particular sentences, #1 makes my intended meaning more clearly than does #2.
Best wishes, Clive