串错了字 twoice --> twice
Once 代表一次,曾经,一旦
-- 副词 adverb
-- 名词 noun
-- 连接词 conjunction
1) I see them once every two months.
2) Once is enough.
2) Once you get into a bad habit,you'll find it hard to get out of it.
Twice 代表两次,两倍
-- 副词 Adverb
1) He comes to work twice a week.
2) The dining-room is twice as big as the kitchen.