threes sounds like freely adv.
in a willing and generous way:-
eg:-The book is now freely available.
eg:-The red wine flows freely !!
eg:-We freely admit that good things come in threes.
A.in + N數字s指「以該數字為計算單位;N個為一組的人事物」。原則上,是可用ones, twos, threes……twelves…直到.hundreds, thousands, millions,只是有些數字單位使用頻率很高,但有些就較少 (譬如: sevens; thirteens..就少),如以下例句: Good things come in threes. (以三為計算單位;三個一組的人事物) Bad things happen in threes " is what everyone said.