"It's" or "Its"?
Writers at all levels of sophistication confuse the two words. "Its" is the possessive case of "it" (i.e., "its" means "belonging to it"). "It's" (with an apostrophe) is the contraction of "it is." Here are a few examples:
wrong: Its important to remember that the population of North America in this period was less than 10 million.
right: It is [or it's] important to remember that the population of North America in this period was less than 10 million.
wrong: A coniferous tree continually sheds it's leaves.
right: A coniferous tree continually sheds its leaves.
A good way of remembering this important distinction: "His" is the possessive form of "him." "He's" is the contraction of "he is." As in the case of "it" the conjunction, but not the possessive case, employs an apostrophe. Writers generally know whether "he's" or "his" is more appropriate in a particular sentence: the words are not homophones (they don't sound alike) and are therefore less easily confused. Every time you come across an "it's" or "its" in your own writing substitute a "he's" or "his" (depending on which form fits grammatically). If "his" makes the sentence grammatically correct you should use "its." If "he's" makes more sense you should use "it's."
Using the above examples:
The first sample sentence (above) is grammatically incorrect: Its important to remember that the population of North America in this period was less than 10 million.
Substitute "he's" and "his" for "Its":
He's [he is] important to remember . . .
His important to remember . . .
The first of the two substitutions makes the most sense. This means that the sentence calls for the contraction "it's." You know that the sentence ought to read
It's important to remember . . .
or
It is important to remember . . .
Practice Sentences
Decide whether the sentence calls for "it's" or "its."
1. She was happy with the paper's content, but was relatively concerned about (it's its) layout.
2. I was wondering if (it's its) possible that she lost track of time.
3. Are you certain (it's its) her priority right now?
4. The program seemed very organized in principle; (it's its) drawback was that it failed to consider the problems encountered by putting good principles into practice.
5. I fail to see how (it's its) any different than before.
6. (It's Its) not a matter of really wanting to own a pet: what is really important is being able to provide for (it's its) needs.
7. She thinks (it's its) about time they agreed to a settlement.
8. The artifact was discovered in a medieval castle in England, but (it's its) origin is unknown.