1. Adding s, as in dogs and cats.
2. Adding es, as in peaches.
3. Adding an apostrophe and s, used in forming the plurals of letters, as in t‘s.

Of course, there are some irregular words that do not comply with any of the above rules, such as goose and its plural geese, and moose and its plural moose.

What seems to be the most common error involving the formation of plurals is the use of an apostrophe and s for forming the plurals of regular words. The apostrophe is only correct when forming the plurals of letters and dates. For any other words, it is incorrect. Thus, writing the plural of apple as apple’s–instead of apples–is considered poor English and should be avoided. Of course, keep in mind that apostrophes do serve a couple of other purposes, one of which is to show possession. In such a case, using an apostrophe to write the apple’s peel would be completely correct.

I often receive e-mails that begin with the following greeting: “Hi Rachel.” Although this is certainly a friendly way to begin a letter, it violates one of the many comma rules: Always use a comma when directly addressing someone/something, regardless of whether the direct address is at the beginning or end of the sentence. If the direct address is in the middle of a sentence, use a pair of commas to set off the direct address.

Note the placement of commas in the example sentences below:

Example 1: Ladies and gentlemen, may I have your attention please? (Direct address at beginning of sentence)

Example 2: It was a pleasure to meet you, Sir. (Direct address at end of sentence)

Example 3: Thank you, my fellow grammarians, for remembering to use correct English. (Direct address in middle of sentence)

So, you see, the salutation “Hi Rachel” should be “Hi, Rachel.” A comma is needed between Hi and Rachel because it is a direct address.

Keep sending the e-mails my way, but remember that I’ll be on the lookout for any missing commas.

When combining two sentences into one compound sentence, a comma and a coordinating conjunction (and, but, or, nor, for, so, yet) are used.

Example 1: The festival was to be held today, but it was canceled due to the rainy weather. (comma and coordinating conjunction)

Sometimes writers use words such as however, furthermore, and therefore (these are called conjunctive adverbs) in place of coordinating conjunctions to combine two sentences into one. This is where a punctuation problem often arises. The mistake writers make is to incorrectly place a comma in place of a semicolon before conjunctive adverbs, as illustrated in the sentence below:

Example 2: The festival was to be held today, however, it was canceled due to the rainy weather. (comma preceding the conjunctive adverb – INCORRECT. Note: The comma following the conjunctive adverb is perfectly correct and should be left as is.)

A semicolon, rather than a comma, should precede conjunctive adverbs when they link two complete sentences. Note the corrected form of Example 2 below:

Example 3: The festival was to be held today; however, it was canceled due to the rainy weather. (semicolon preceding the conjunctive adverb – CORRECT)

Don’t be misled–there ARE situations in which it is entirely correct to use a comma before a conjunctive adverb, as in the following sentence:

Example 4: The sporting events, however, continued despite the weather.

Note that in this sentence, in contrast to the sentence in Example 3, no semicolon is needed because it is not a compound sentence.