"Oh!" he said brightly; he understood now. Potions. He wouldn't have made the jump from potions to sciences, if he were trying to describe it himself, but the laboratory couldn't really have been anything else, he didn't think. Unless Lestrange was talking about alchemy — that might have had more of a laboratory-feeling, but was also just Fancy Potions, as far as Ford was concerned, so either way he thought he got the gist.

"Are you planning to make a career out of laboratory work when you stop... uh, what you're doing now?" he asked; at the last minute he'd forgotten what euphemism they had previously used for Quidditch, and didn't want to try to make up a new one in case he accidentally confused Lestrange. The Muggles would also probably think this was a crazy conversation if he kept jumping around so much, but — well, they probably thought that anyway, with his being so vague about his career.