Thorne, if you do not know the husband is being unfaithful, you would be very unwise to mention it, especially if not asked. I don't think it is any kind of lie, unless it is what sleeping dogs do.

For it to be a lie of omission, you must deliberately refrain from confirming the wife's suspicions.

IMHO, that is.

Ozme, are you really trying to deceive the client by not admitting to a headache? Or are you simply rehearsing formalities? After all, if you said, "Oh, I have a headache," wouldn't the client simply respond, "I'm sorry to hear it," and then move on to inspect your price list?

Now, if you had bubonic plague, and still said "Fine," that would be a lie of omission.

IMHO.