Unalloyed means pure — with nothing mixed in to weaken or spoil it. It comes from metals: an alloy is a mixture of metals, so unalloyed gold is gold with nothing added. But in everyday English almost nobody uses it about metal any more. It lives now in front of good feelings and good things: unalloyed joy, unalloyed pleasure, unalloyed delight, unalloyed success, unalloyed admiration. The mixing idea is still doing the work. When we are happy, our happiness usually has something else stirred into it — worry, regret, a but. Unalloyed joy is joy with none of that in it. This is why the word appears so often in the negative, and that is worth noticing: 'the evening was not an unalloyed success', 'her feelings were not unalloyed pleasure' are polite English ways of saying something went partly wrong. If you hear 'not unalloyed', expect a criticism underneath the good manners. The word is formal and literary; a student writing an email should say 'pure' or 'complete'. It goes before nouns, and it strongly prefers abstract ones — feelings and outcomes — so unalloyed happiness sounds natural while unalloyed water does not.

純粹的、毫無雜質的（喜悅、成功等）。原本講金屬沒摻別的，現在幾乎只用在抽象的好事上。常見的 not an unalloyed success 是客氣話，意思是「其實有問題」。