Learn English – I need clarification on the use of the word “either”

grammarword-usage

In two different text the first one I used to "combine" the elements in the "or" sentence in the other I only have 2 choices.

Both sentences are from boardgames:
"Play if at least 3 Imperial systems contain EITHER a sabotage marker or a Rebel unit"

In my understanding this can be used (play) when I have 2 sabotage marker and 2 rebel units on Imperial systems.

The second one:
"You may EITHER exchange your cards with another player or discard any number of cards and draw en equal number of cards"

In this case the rulebook clarify the ruling saying you "CHOOSE" one action.

I think the key is in the "or" placement in the second one you select actions in the first one items that can be combined.

If I'm wrong in my interpretation (I'm not English native) excuse me and thanks for any help in this matter if I'm correct: Is the wording in the first one ambiguous or bad wrote?

Thanks again

(In forums about rules of the first game the community say this is a correct use combining BUT my friend don't like it because the "either" word about choices I tell him is about "grammar" or phrase construction not about only that word, even some "people that knows English" say he is right but, as we, not English natives)

Best Answer

In Latin, "vel" is a non-exclusive "or" whereas "aut ... que" is an exclusive "or." English is not so clear-cut. Many people view "A or B' as ambiguous between exclusive and non-exclusive meanings. If you want to avoid risk of ambiguous interpretation, I suggest writing or saying:

(Non-exclusive "or") "A or B or both;"

(Exclusive "or") "Either A or else B."

I have known, however, careful speakers who intend an exclusive "or" when saying "either A or B," and who intend a non-exclusive "or" when saying "A or B." They may be strictly correct, but I prefer to avoid the possibility of misinterpretation.