measure word, noun, numeral · classifier for bites, sips, or things taken into the mouth

他喝了一口水。

measure word, noun · classifier for family members, domestic animals, and objects with openings such as cannons or wells

他家有五口人。

noun, directional, expression, place word, punctuation · the opening through which an animal or human takes in food

他张大着口，还没回过神来。

place word · entrance, exit, or opening of a place like a valley, a street, or a tunnel

他就在胡同口等着你。