ON A long, boring drive, I got to talking about calendars with my brother, since the Jewish new year (Rosh Hashanah) was about to arrive. It wasn't so much as a conversation as a monologue; I became briefly obsessed by different cultures' calendars once, and learned everything I could about them. I told him that Muslims have a lunar calendar, which means their year is shorter than the Gregorian one (about 354 days). So Ramadan (for example) travels throughout the Gregorian year. The Jewish calendar is also lunar, but the holidays stay in place. Passover is always in the spring, the high holidays (Rosh Hashanah and Yom Kippur) always in the fall. How do they stay there? "Because of..."
I stopped. I knew a word that one might only have one or two opportunities to use in a lifetime, when boring someone on the motorway about calendars. "...intercalation," I wanted to say. Or, as the OED explains, "The insertion of an additional day, days, or month into the ordinary or normal year." The addition of February 29th every four years is intercalation. So is the addition of days to the Jewish lunar year to keep the holidays in the right seasons. I thought how frighteningly satisfying it would be to use this precise word.
But I stopped, realising that my brother probably didn't know it. (He's an educated and very smart man, but not the type to sit in front of a computer reading about calendars.) For me to say "intercalation" and not explain it would be irritating; it's bad form to use a word you're pretty sure the other person doesn't know. And for me to say it and then explain it would be pedantic. So I backtracked: "the months stay in place because they add the occasional month to the calendar to make sure they do."
What a shame. I don't like big words to replace ordinary words. But it's incredibly gratifying to have just the right one to hand, the word as precise as a needle. To have the word and not to be able to use it, though, was a minor torture. In writing, this isn't a problem; you can go on and use "intercalate", and let your readers will either understand it or look it up. But what to do in conversation? Readers with etiquette tips (or other ultra-precise words they wish they had more opportunities to use), let us know.