The noun 入口 (rùkǒu) means 'entrance' or 'entry point.' It is composed of 入 (to enter) and 口 (opening/mouth), and can refer to both physical entrances to places and metaphorical entry points. For example, 公园入口 means 'park entrance.'
请在公园入口集合。
Qǐng zài gōngyuán rùkǒu jíhé.
Please gather at the park entrance.
地铁站的入口在大楼的右边。
Dìtiě zhàn de rùkǒu zài dàlóu de yòubiān.
The entrance to the subway station is on the right side of the building.
入口处排了很长的队。
Rùkǒu chù pái le hěn cháng de duì.
There was a very long line at the entrance.