Overcrowding is the problem itself: the situation when too many people or too many things are packed into one place. Overcrowded describes the place; overcrowding names the state.

Overcrowding這個詞 is指的就是 the problem itself問題本身：when當 too many people太多人 or或 too many things太多東西 are packed into被塞進 one place一個地方時 the situation的情況. Overcrowded這個詞 describes描述的是 the place地方本身；overcrowding指的則是 the state這種狀態.

You hear it about cities, classrooms, hospitals, animal shelters, and public transport.

You hear it about你常會聽到這個詞用在 cities城市、classrooms教室、hospitals醫院、animal shelters動物收容所、and public transport和大眾運輸上.

It is a little more formal than saying 'it is too full,' so news, reports, and school writing use it a lot — though people say it in speech too. It is a noun, so you talk about overcrowding, or the overcrowding in a place.

It比起 is a little more formal要正式一點 than saying比起說 'it is too full,'『太滿了』這種說法 so所以 news新聞、reports報告、and school writing和學校作文 use it a lot很常用它 — though不過 people say it in speech too口語裡人們也會這樣說. It它 is a noun是名詞，so所以 you talk about you talk about overcrowding你會說overcrowding這個字, or或 the overcrowding in a place某個地方的overcrowding.

Though actually, English speakers sometimes slide between the noun and the adjective, but in careful writing they are not the same job.

Though actually不過其實, English speakers英語使用者 sometimes有時候 slide between會混著用 the noun and the adjective名詞和形容詞, but但 in careful writing在講究的寫作裡 they are not the same job這兩者的功能並不一樣.