I've got to admit I've always found 'on the left/right' and 'to the left/right' expressions rather confusing. I'd like to learn to use them correctly. I've made up some examples, and I'd be garteful if anybody could tell me if there's any problems with them.
1. There is an armchair to the left of the sofa.
2. There is a stain on the left of the book cover.
2. Dewey is on Louie's right.
3. Dewey is on the right of Louie.
4. Huey is to Louie's right.
5. Huey is to the tight of Louie.
6. Dr. Brown is standing to my left.
7. Dr. Brown is standing on my left.
Thank you in advance.
I feel that there is normally no difference between 'to' and 'on' - if no movement is involved. When there is clear movement, then it must be 'to':
Move to the left of John.
Note this example:......Take the next road to/on the left.
Although the person addressed will be moving into the road as s/he turns (to the) left, the road itself is not moving to the left, hence the free choice.
In all your sentences except #2, both 'to' and 'on' are possible. In #2, however 'on' suggests to me that the book cover itself is stained, whereas 'to' suggests to me that something on/to the left of the book is stained.