If something is preventive, it is meant to stop a bad thing before that bad thing starts.

If something如果某樣東西 is preventive是preventive, it它 is meant to stop目的是要阻止 a bad thing一件壞事 before that bad thing starts在那件壞事發生之前。

People use this word a lot about health: preventive medicine tries to keep you well, so you do not have to be treated later. Cleaning your teeth, a vaccine, and wearing a seat belt are all preventive in that way. Offices and governments also talk about preventive measures — extra steps taken because someone is afraid a problem might come.

People有人 use this word a lot很常用這個字 about health談健康的時候: preventive medicine預防醫學 tries to keep you well想讓你保持健康, so所以 you你 do not have to be treated later之後就不用被治療。Cleaning your teeth刷牙, a vaccine打疫苗, and wearing a seat belt繫安全帶 are all都是 preventive在這個意義上都是preventive in that way。Offices and governments機關和政府 also talk about也會談到 preventive measures「預防措施」 — extra steps額外採取的步驟 taken because someone is afraid因為有人擔心 a problem might come問題可能會發生。

You will hear it in careful talk more than in very casual chat. Though actually, many everyday speakers say preventative instead. The two words carry the same idea; medical writing often prefers the shorter one, preventive.

You你 will hear it會...更常聽到它 in careful talk more than in very casual chat在講究的談話裡比在很隨性的閒聊裡。Though actually不過其實, many everyday speakers許多日常說話的人 say preventative改說preventative instead。The two words這兩個字 carry the same idea帶著同樣的意思; medical writing醫學寫作 often prefers通常比較偏好 the shorter one比較短的那個, preventive「preventive」。

It can also be a noun, 'a preventive', meaning a thing (often a medicine) meant to stop trouble — a little more formal, and less common than the adjective.

It它 can also be也可以當 a noun名詞, 'a preventive'「一種預防物」, meaning指的是 a thing (often a medicine)一樣東西（通常是藥物） meant to stop trouble目的是要阻止麻煩 — a little more formal稍微正式一點, and而且 less common than比形容詞少見 the adjective。