One of the biggest and most often-committed crimes against the English language these days is folks who do not know the difference between a possessive noun and a plural noun.
Heavens to Betsy! Some of the folks who commit this noun faux pas are juniors and seniors in college or graduate students. They should have learned this in 6th grade but apparently they were too busy texting to pay attention in class that day. (Oops, now I’m meddling!)
Let’s take it from the top. Here is the possessive form of the word “customer:”
customer’s boat (one customer has a boat)
customers’ boat (two or more customers have one boat)
customers’ boats (two or more customers each have a boat)
The thing they all have in common is that they (the customers) all possess something, hence the possessive apostrophe.
In my parentheses in the last sentence, I showed you the plural form of the word “customer.” Using the word “customers” means that you have more than one customer (the single form of the same word).
While we’re here, let’s talk about how to address our customers (plural) using pronouns. (Yes, this is a slight digression but these mistakes also happen with about the same frequency or even more often that the dilemma of possessive versus plural in the world of recalcitrant nouns).
If you have one customer, you should refer to the person as he or she, depending on your observation (this is becoming increasingly difficult. I understand and feel your pain.) If you don’t know, either by appearance or name if the person is male or female, refer to the person as he or she (or him or her, depending on the context). The sentence would look like this:
If the customer comes in to complain, tell him or her that we will take care of it for him or her. Do NOT say “we will take care of it for them.” You have just split the person in half, making him or her into two people. Ouch!
The way around the he/she or him.her dilemma is to refer to “customers” and then use the word “they.” Here is the example:
If our customers come into complain, tell them that we will take care of it for them. (You better, too, because you won’t have customers very long if they are complaining about you.)
I hope this helps. Do you have a specific problem with English? Make a comment and let me know how I can help you.