Thanks for all of the super-prompt and helpful responses.
They do, though, raise for me a secondary (pun intended) question: What, exactly, does one do that makes it count as secondary fermentation? Just re-rack with a bit more corn sugar? Or just re-rack?
Thanks!
Ah, you've hit on the million dollar question!
In a brewery, there is NO "secondary fermenter". None. The fermentation takes place in the fermenter, and then is pumped to the "bright tank" for clearing. That's primarily so a new batch can be started in the fermenter, not because of anything magical that happens in moving the beer.
However, I'm an old winemaker. In winemaking, there is a primary, and then you move the wine to "secondary" where the fermentation finishes under airlock.
My belief is that homebrewers took winemaking techniques and applied them to brewing, and kept some of the same terminology.
But in winemaking, you normally do the primary not under airlock, and stir the wine for the first few days, so it's a hyrbridized technique.
When more people starting homebrewing, and realized that there is no such thing as a "secondary fermentation" with beer, then people starting rethinking that. The holdouts now tend to be people who read books that describe a secondary and the need to get the beer off of the yeast cake, or old winemakers in homebrew shops.
The current thinking, from maybe the last three or four years, is that a transfer to a clearing vessel ("bright tank") is not necessary for homebrewers, but some still choose to do it.
Gravity is what clears the beer, and not the act of moving the beer to another container.
Sometimes I transfer, because for lagers I always do. Or to oak a beer, or because I want to reuse the yeast for another batch. But it's not necessary for most homebrews.