I'm certain that I locked the door before leaving.（我确定我在离开前锁了门。）

She is certain to win the competition because of her hard work.（由于她的努力，她肯定会赢得比赛。）

There is a certain charm about this old town.（这个古镇有某种独特的魅力。）

We need to finish this task within a certain time limit.（我们需要在一定的时间限制内完成这项任务。）

He has a certain talent for music that shows even at a young age.（他即使在很小的时候就展现出了一定的音乐天赋。）

Are you certain of his whereabouts?（你确定他在哪里吗？） Certain plants can only grow in specific environments.（某些植物只能在特定的环境中生长。）

I have a certain feeling that something good is about to happen.（我有一种预感，好事即将发生。）

The rules state that there are certain conditions for entry.（规则规定有一些特定的参赛条件。）

They made a certain amount of progress in their research.（他们在研究中取得了一定的进展。）

You should be certain of your facts before making a statement.（在发表声明之前，你应该对事实有把握。）

Certain animals hibernate during the winter months.（某些动物在冬季会冬眠。）

There's a certain sadness in her eyes that I can't ignore.（她眼中有一种无法忽视的悲伤。）

We must follow certain procedures to ensure safety.（我们必须遵循一定的程序以确保安全。）

He has a certain way of making people feel comfortable around him.（他有一种能让周围人感到自在的本事。）

Is it certain that the meeting will be postponed?（会议肯定会推迟吗？） Certain diseases can be prevented through vaccination.（某些疾病可以通过接种疫苗来预防。）

She has a certain elegance in the way she walks.（她走路的姿态有一种优雅的气质。）

We need to set aside a certain amount of money for emergencies.（我们需要留出一定数额的钱用于应急。）

There are certain things in life that money can't buy.（生活中有一些东西是金钱买不到的。）