Why is it when someone dies, we offer our condolences, in plural? Can’t we just offer our condolence and have that be sufficient? Are we trying to unconsciously make it sound better by making it plural? If so, then why do we offer our sympathy, and not our sympathies? We don’t say, “You have my sympathies!”
I’m not trying to make anyone paranoid about what to say at such a difficult time. It’s hard enough as it is to say anything that adequately expresses our sentiments – mere words seem to fall flat in these situations.
“Condolence” comes from the Latin condole which means to suffer together. As such, it certainly is an appropriate word for expressing grief over a death. As for its employment mostly in the plural form, this seems to simply be a matter of historical usage. Prior to the nineteenth century it was mostly used in the singular. If you’d like to be a trendsetter (or a traditionalist?), it is perfectly legitimate to offer either condolence (in the singular) or even sympathies (in the plural). If nothing else, your sentiment will stand out from the many others the bereaved will receive.