www.alphadictionary.com

• penance •

Pronunciation: pen-nêns • Hear it!

Part of Speech: Noun, mass (no plural)

Meaning: Pain, suffering, or self-mortification in expectation of forgiveness of some evil that we have committed.

Notes: Today's Good Word is often confused with penitence "regret for wrong-doing". Penance is a step beyond penitence; it is some act of mortification or contrition intended to show penitence. It is a lexical orphan except for possibly penanceless. As a mass noun, it doesn't even have a plural.

In Play: The idea of penance might seem to have originated in the Church: "My confessor imposed a penance of 100 Hail Marys and 10 hours of community service in the soup kitchen for keeping the money I found in the park." But imposing penance is a general punishment; we do it all the time: "Clifford, you have to do the dishes tonight in penance for that remark about too much salt in the saltimbocca."

Word History: Today's Good Word comes from Medieval Latin penitens "repenting", the present participle of penitere "to repent". This word was borrowed originally as penitence which later devolved into penance. Scholars later discovered the original and reintroduced it, but penance remained with a distinct meaning. Both are related, of course, to penitentiary, which our Puritan ancestors considered a proper place of penance, designed to help criminals regain their sense of moral rectitude.

I've seen and heard the plural often: "penances". Perhaps
it is not good grammar, but it is used.

As mentioned in the notes, it doesn't even have a plural. So if you see 'penances' they are not aware of the correct grammar.

Sorry to disagree, but all the dictionaries I have checked allow the use of "penance" as a countable noun. Some explicitly state that it can be countable. Wiktionary includes "penances" as a legitimate word:

http://en.wiktionary.org/wiki/penances

Penance does not of necessity require pain nor suffering. Nor must it be thought of as punishment. Surely it is related to penance, but may demonstrate repentance in action. One's repentence may evoke the penance of repaying the community for his ill-treatment by volunteering twice a week at a soup kitchen.

And the typical Roman tradition after confessing
one's sins (at least in the movies) is
'recite three Our Fathers and three Hail Marys',
is hardly punishment.