expressing intersection and union in English

[wld8db8]

A. clocks that are designed by XYZ and runs backward
B. clocks that are designed by XYZ and that runs backward.
C. clocks that are designed by XYZ and those that runs backward.

Which of the above three corresponds to the intersection of {clocks that are designed by XYZ} and {clocks that runs backward}, i.e. clocks designed by XYZ that also runs backward? And which corresponds to the union, i.e. clocks that are designed by XYZ or runs backward or both?

My guess is
A. intersection
B. intersection
C. union
But I'm not 100% sure.



how do you refer to the intersection of {small clocks} and {round clocks} and how about the union?

1. small, round clocks
2. small round clocks
3. small and round clocks
4. small clocks and round clocks
5. small or round clocks.

My guess is
1. intersection
2. intersection
3. ambiguous
4. union
5. union

Not 100% sure on that either.

[Monticello]

Hi wld8db8,

Let's take this brief wiki article on set theory as a point of reference here. (I cite wiki here not as any ultimate authority, but as a readily available, and -- for the purpose of your question here -- reliable online source.)

A. clocks that are designed by XYZ and runs run backward
B. clocks that are designed by XYZ and that runs run backward.
C. clocks that are designed by XYZ and those that runs run backward.

Which of the above three corresponds to the intersection of {clocks that are designed by XYZ} and {clocks and that runs run backward}, i.e. clocks designed by XYZ that also runs backward? Yes. And which corresponds to the union, i.e. clocks that are designed by XYZ and/or all clocks that runs run backward (i.e., whether or not these backward running clocks are designed by XYZ)? or both? Yes. (Please note: While the conjunction combination, and/or, should be avoided in everyday English usage, it is indispensable when discussing either set theory or Boolean algebra).

My guess is
A. intersection Yes.
B. intersection Yes.
C. union Yes.
But I'm not 100% sure. Hope you are now.

how do you refer to the intersection of {small clocks} and {round clocks} and how about the union?

1. small, round clocks
2. small round clocks
3. small [clocks] and round clocks - is implied here
4. small clocks and round clocks
5. small or round clocks.

My guess is
1. intersection Yes.
2. intersection Yes.
3. ambiguous union
4. union Yes.
5. union Yes.

Not 100% sure on that either. 80% ain't too bad.