Missing or misplaced apostrophe
Generally, show possession by adding 's (apostrophe + "s") to nouns:
Charlie spent the day watching childrens television shows.
Problem and cure: To show possession, an apostrophe should be inserted between the "n" and the "s": children's.
Like most usage rules, this one has exceptions:
1. Never use an apostrophe with possessive forms of personal pronouns ("hers," "his," "ours," etc.):
He transferred the funds from his account to ours.
2. There is no need for an extra "s" with plural nouns already ending with the letter "s":
Both of the dogs' bowls were empty.
3. Names from antiquity that end with the "eez" sound do not need an extra "s":
Harriet read all of Sophocles' plays and all but one of Aristophanes'.
4. It is standard to add an additional "s" to other names, whether they end with "s" or not:
Elvis's peanut butter and jelly sandwich lay on the table.
William Carlos Williams's poetry was greatly influenced by Walt Whitman's.