两个都是方位词。 1）表示级别、次序、数目等在某一点之上或之下。 2）指代前面说过的或下面要说的话，偏书面语。

Structure

Examples

我老家空气还不错，PM2.5 一般在五十以下。Wǒ lǎojiā kōngqì hái bùcuò, PM2.5 yībān zài wǔshí yǐxià.The air in my hometown is good. PM 2.5 is generally under 50.
我们需要有两年以上工作经验的人。Wǒmen xūyào yǒu liǎng nián yǐshàng gōngzuò jīngyàn de rén.We need people with two years of working experience or more.
十岁以下的孩子不用买票。Shí suì yǐxià de háizi bùyòng mǎi piào.Children under the age of 10 do not need to buy tickets.
我们出差都住三星级以上的酒店。Wǒmen chūchāi dōu zhù sān xīngjí yǐshàng de jiǔdiàn.When we go on business trips, we stay at hotels with at least a 3-star rating.
这里的冬天气温都在零度以下。Zhèlǐ de dōngtiān qìwēn dōu zài língdù yǐxià.This winter, the temperature has been less than 0 degrees.
以下就谈谈这个问题应该怎么解决。Yǐxià jiù tántán zhège wèntí yīnggāi zěnme jiějué.In the following conversation, we will discuss how we should resolve this problem.
以上只是我个人的看法。Yǐshàng zhī shì wǒ gèrén de kànfǎ.The following is just my personal opinion.

以内 and 以外

以内：方位词。在一定的时间、处所、数量、范围的界限之内。以外：方位词。在一定的时间、处所、数量、范围的界限之外。"以外"常常跟"除了"连用。

Structure

Examples

两天以内必须完成。Liǎng tiān yǐnèi bìxū wánchéng.Must be completed in two days or less.
半小时以内能送到吗？Bàn xiǎoshí yǐnèi néng sòngdào ma?Can you deliver in 30 minutes or less?
这个大楼 50 米以内不能停车。Zhège dàlóu wǔshí mǐ yǐnèi bù néng tíng chē.You cannot park within 50 meters of this building.
请你站在两米以外的地方。Qǐng nǐ zhàn zài liǎng mǐ yǐwài de dìfang.Can you stop 2 meters outside of this place?
这个区以外的几个区都不太发达。Zhège qū yǐwài de jǐ gè qū dōu bù tài fādá.All of the areas outside this one are not very developed.
除了三四年级的学生以外，五年级的学生也可以参加。Chúle sān sì niánjí de xuéshēng yǐwài, wǔ niánjí de xuéshēng yě kěyǐ cānjiā.Aside from the students in Grade Three and Grade Four, students in Grade Five can also participate.

以上 and 以下

以内 and 以外