• To form the plural of letters and numbers.

The teacher made sure we crossed our t's and dotted our i's. The child learned his ABC's before he was three years old. World War II was still going on in the 1940's.

Remember: don't make regular words plural by adding an apostrophe and "s", only use the apostrophe and "s" to make numbers and letters.

Writing a Good Sentence

It doesn't matter how much you learn about the rules of grammar if you don't use them. When you try to learn grammar, your goal should be to improve your writing to make it easier for others to understand the idea you're trying to get across. When you change the structure of a sentence, pile too much information into a sentence, use only parts of a sentence or jam two different sentences together, you make it hard for the reader to understand you. In this section, we will look at mistakes that everyone makes from time to time and how to correct them.

Keeping Structure the Same when Ideas are Similar

When you write a sentence, you should try to keep things equal. If you use one form of a verb in one part of a sentence, you should use the same form of the verb in the other part of the sentence if the ideas are similar. This usually happens in longer sentences, but can also happen in short ones.

He likes reading and to write on the computer.

If you look at the first underlined word, you see that it ends in "ing". The second underlined word is similar to the first (they are both things that he does using a computer). But the second words are written differently than the first. The sentence should look like this:

He likes reading and writing on the computer.

Or

He likes to read and to write on the computer.