If something is prepaid, the money has already been given before you need the thing or use the service.

If something is prepaid如果某件東西是prepaid（預付）的，before you need the thing or use the service在你需要那樣東西或使用那項服務之前，the money錢 has already been given早就已經付了。

A prepaid envelope has the postage paid. A prepaid phone or prepaid SIM has credit on it before you call. Hotels, trips, and school fees can all be prepaid.

A prepaid envelope預付的信封 has the postage paid郵資已經付好了。A prepaid phone or prepaid SIM預付手機或預付SIM卡 before you call在你打電話之前 has credit on it裡面就已經有預付的通話額度。Hotels, trips, and school fees飯店、旅遊行程和學費 can all be prepaid都可以預付。

It is ordinary in shops, phones, and forms.

It它 is ordinary很常見 in shops, phones, and forms在商店、手機和各種表格上。

The opposite in phone plans is often postpaid: you use first, then pay a bill. Though actually, British “pay as you go” phones are prepaid — you put money on first — which confuses learners who hear pay as you go and think they pay later.

The opposite in phone plans手機資費方案裡的相反詞 is often通常是 postpaid「postpaid」（後付）: you use first你先用，then pay a bill之後再付帳單。Though actually不過其實，British "pay as you go" phones英國的「pay as you go」手機 are prepaid其實是預付的 — you put money on first你要先儲值 — which confuses learners讓學習者感到困惑 who hear pay as you go他們一聽到pay as you go and think they pay later就以為是之後才付錢。

And prepaid does not mean free. Someone paid; it just was not you, or not at the moment of use.

And而 prepaid prepaid does not mean free不代表免費。Someone paid有人付了錢；it just was not you只是不是你，or not at the moment of use或不是在使用的當下付的。

You will hear the adjective prepaid far more than the verb prepay.

You你 will hear會聽到 the adjective prepaid形容詞prepaid far more than遠比 the verb prepay動詞prepay要多得多。