yǐ xià
气温已降到零度以下
Qìwēn yǐ jiàng dào líng dù yǐxià.
The temperature has dropped below zero degrees.
请勿携带三岁以下儿童入场。
Qǐng wù xiédài sān suì yǐxià értóng rùchǎng.
Please do not bring children under three years old into the venue.
以下就要谈谈具体办法。
Yǐxià jiù yào tántán jùtǐ bànfǎ.
Below we will discuss specific measures.