1. I have seven balls. One is white, another is black, a third is blue, a fourth is green, a fifth is brown, a sixth is pink, and the other is orange.
(Is this sentence grammatical and commonly used?
2. I have two balls: One is green and the other is yellow.
3. I have two balls: one is green and the other is yellow.
(Do we have to use a small letter 'o,' or do we have to use the capital letter 'O'?)
4. I have two balls; one is green and the other is yellow.
(When a semi-colon is used, we have to use 'one.' Am I right?
For 1, I'd just list the colors, not "one is" etc.
2 is correct.
3 is incorrect; see your other post.
4 is incorrect; see your other post and this webpage about using semicolons: http://grammar.ccc.commnet.edu/grammar/marks/semicolon.htm
1. Yes, the sentence you provided is grammatically correct and commonly used to describe the colors of the balls.
2. The sentence "I have two balls: One is green and the other is yellow" is also grammatically correct and commonly used.
3. In this case, it is more common to use a lowercase 'o' in "one" rather than a capital 'O.' So the sentence "I have two balls: one is green and the other is yellow" is correct.
4. Yes, when using a semicolon, it is common to use "one" instead of "1". So the sentence "I have two balls; one is green and the other is yellow" is correct in this context.