What is a good mnemonic rule that an English learner can use to remember the difference between its (possessive adjective: a team has started its lunch) and it's (verb: it's raining)?
I'm not sure of how good a mnemonic this is, but it's always worked for me. When proofreading, I simply remind myself:
So, when I say:
I recognize that "It's" means "It is", so I leave the apostrophe in. But when I type and proofread:
I realize that "it's" does not mean "it is"; it means "the foundation belonging to it", so I remove the apostrophe:
If you don't like my method, it's easy to find lots more on the subject.
You just know that it's stands for it is, two words.
When reading, you just see if it is a single word or two words "linked" with an apostrophe.
For writing, you may employ this mnemonic:
A tear will resemble to write it with an apostrophe.
This is a new answer (Jan 2015) to a two-year old question (Jan 2013).
I revived this thread because I believe this provides a best-of-class answer that complements the well-deserved selected answer by J.R.. It's a tall order to come in so late with such a bold statement. I only ask that as you assess the value of this answer (for better or worse!), to keep in mind that this is relatively new, and so this has not received the same benefit of attention as answers given two years ago when the question was first asked.
Until now, there has been no gold standard, easy-to-remember mnemonic that helps someone generate the correct form-to-meaning of its vs. it's. So I created a mnemonic device specifically for this answer. It's short, clear, and easy-to-remember.
This is the mnemonic device:
That's it! That's the mnemonic device:
Just look at it (below). Doesn't that look like a pronoun? Followed by apostrophe S? Is that so hard?
it 's pronoun apostrophe S It's a pronoun followed by apostrophe S.
Let's do that again.
Put it all together!
Explain it please!
This mnemonic should be spread to the four corners of the English speaking world!
Its and my is "just one word".
If I can substitute its (one word) with another possessive adjective my (one word), and the resulting phrase is grammatical then there is no need for the apostrophe e.g.,
"my lunch" is grammatical so no apostrophe is required (the possessive adjective, its, is 'just one word'.)
When we substitute it's raining (or its) with my we get:
"My raining" as a phrase is not grammatical so it's is the correct spelling (two words; it + is)
Further examples: (thinking 'yes' or 'no' for grammatical and ungrammatical)
The company has lost my licence ----> grammatical ---> my ('just one word') ---> its
Check to see if my gone ----> ungrammatical ---> we need two words ---> it's (it + has)
... chases my prey through the coral ----> grammatical ---> my ('just one word') ---> its
This isn't my book, my Fernando's. ----> ungrammatical ---> we need two words ---> It's (It + is)
The dog is eating my dinner ----> grammatical ---> my ('just one word') ---> its
Another not-quite-mnemonic method of remembering. This may not be helpful to people who have no exposure to English poetic forms:
I learned to keep them straight by keeping in mind the poetic form, 'tis.
It's is ..... the same as 'tis.
These all mean the same as it's. Conveniently, they are written with the same four characters, rearranged - move the apostrophe and the t to the front, and you go from it's to 'tis.
The possessive its is not a synonym for 'tis, so it cannot be rearranged in the same way, so it doesn't have an apostrophe.
So the "mnemonic" is again:
It's is ..... the same as 'tis.
Emphasize the bold parts to give it a lilting rythm.
Make up your own exercise of the type thing + part of it. Model
1 a house has a roof - Change it to: the house and its roof
2 the book and its price
3 the bag and its contents
Make up ten examples of your own. Then I think you won't need a mnemotechnical aid.