An unanticipated event or result is one nobody expected — nobody saw it coming and nobody planned for it. It is close in meaning to unexpected, but not quite the same in feeling.

An unanticipated event or result一個 unanticipated 的事件或結果 is one nobody expected是沒有人預料到的 — nobody saw it coming沒有人看出它會發生 and nobody planned for it也沒有人為它做準備。It is close in meaning to unexpected意思跟 unexpected 很接近, but not quite the same in feeling但語感不完全一樣。

Unexpected is the ordinary word and can be about anything, good or bad, big or small. Unanticipated is more formal and leans towards situations where somebody was supposed to be looking ahead — a plan, a budget, a study, a risk assessment.

Unexpected是 is the ordinary word是一般常用的字, and can be about anything什麼事都可以用, good or bad不管好壞, big or small不管大小。Unanticipated則 is more formal比較正式, and leans towards situations較偏向用在 where somebody was supposed to be looking ahead本來就該要事先設想到的情況 — a plan計畫, a budget預算, a study研究, a risk assessment風險評估。

So we say 'unanticipated costs', 'unanticipated consequences', 'unanticipated delays'. There is often a faint sense of 'we should have thought of that'.

So因此 we say會說 'unanticipated costs'「unanticipated costs」（未預期的成本）, 'unanticipated consequences'「unanticipated consequences」（未預期的後果）, 'unanticipated delays'「unanticipated delays」（未預期的延誤）。There is often常常帶有 a faint sense of 'we should have thought of that'一種「我們本來應該想到才對」的隱約語感。

Because of that, you meet it most in reports, business writing and research. In everyday speech people just say 'I didn't expect that'.

Because of that正因如此, you meet it most你最常在 in reports, business writing and research報告、商業文書和研究裡遇到它。In everyday speech在日常說話裡, people just say人就直接說 'I didn't expect that'「I didn't expect that」。

You will also meet the very common phrase 'unintended consequences', which is a cousin: unintended means we did not WANT it; unanticipated means we did not FORESEE it. Something can be both, and often is. The word is neutral by itself, but in real use it drifts towards bad news, because when a surprise is good, English speakers usually reach for 'unexpected' or 'a pleasant surprise' instead.

You will also meet你也會遇到 the very common phrase 'unintended consequences'很常見的一句 'unintended consequences', which is a cousin它算是近親: unintended means unintended 的意思 we did not WANT it是我們不想要它; unanticipated means而 unanticipated 的意思 we did not FORESEE it是我們沒有預見到它。Something可以 can be both兩者都是, and often is而且常常兩者都是。The word這個字 is neutral by itself本身是中性的, but in real use但實際使用時 it drifts towards bad news常常偏向壞消息, because因為 when a surprise is good當是好的驚喜時, English speakers英語使用者 usually reach for 'unexpected' or 'a pleasant surprise' instead通常會改用 'unexpected' 或 'a pleasant surprise'。