Adjective, and also a noun. A white-tie event is the most formal kind of social occasion there is in Western dress custom. Men must wear a white bow tie, a black tailcoat (a jacket cut short in front with two long 'tails' at the back), a white waistcoat and a stiff white shirt; women wear a long evening gown. "White tie" written on an invitation is an instruction, not a description.

Adjective形容詞，and also a noun也當名詞。A white-tie event white-tie 的場合 is是 in Western dress custom西方服裝慣例裡 the most formal kind of social occasion there is現有最正式的那種社交場合。Men男士 must wear必須穿 a white bow tie白色領結、a black tailcoat黑色燕尾服（a jacket cut short in front前襬剪短、with two long 'tails' at the back後面垂兩條長「尾巴」的外套）、a white waistcoat白色背心 and a stiff white shirt和硬挺的白襯衫；women女士 wear穿 a long evening gown長禮服。written on an invitation寫在邀請函上的 "White tie" is an instruction是一道指示，not a description不是一句描述。

Because it sits at the very top of the formality ladder, the word is really a measuring stick. One step down is black-tie (black bow tie, dinner jacket / tuxedo) — far more common, and what most people mean by 'formal'. So when someone says "it's white-tie", they are saying: this is grander than a wedding, grander than a company dinner.

Because因為 it它 sits at the very top of the formality ladder坐在正式程度階梯的最頂端，the word這個字 is really其實是 a measuring stick一把量尺。One step down往下一階 is black-tie是 black-tie（black bow tie黑色領結、dinner jacket / tuxedo小晚禮服）——far more common常見得多，and what most people mean by 'formal'也是多數人說「正式」時指的那種。So所以 when someone says "it's white-tie"當有人說 "it's white-tie"，they are saying他是在說：this這 than a wedding比婚禮 grander更盛大，than a company dinner比公司晚宴 grander更盛大。

In real life almost nobody attends one: state banquets, royal occasions, some old university balls, the Nobel Prize ceremony, a few charity balls in New York. Many English speakers have never been to a single white-tie event in their lives.

In real life現實生活裡 almost nobody幾乎沒有人 attends one參加過：state banquets國宴、royal occasions王室場合、some old university balls幾場老大學的舞會、the Nobel Prize ceremony諾貝爾獎頒獎典禮、a few charity balls in New York紐約少數幾場慈善舞會。Many English speakers許多說英文的人 in their lives一輩子 have never been to a single white-tie event連一場 white-tie 的場合都沒去過。

Used as a noun too: "He was in white tie." And people stretch it as a joke or an exaggeration — "this isn't a white-tie affair, just come as you are" — meaning don't worry, it's casual. Note the hyphen appears before a noun (a white-tie dinner) but usually not after the verb (the dinner is white tie).

Used as a noun too也當名詞用："He was in white tie."他當時穿著 white tie。And people stretch it人們也會把它拉寬 as a joke or an exaggeration當玩笑或誇飾——"this isn't a white-tie affair, just come as you are"這不是 white-tie 的場合，平常怎麼穿就怎麼來——meaning意思是 don't worry, it's casual別擔心，穿輕鬆的就好。Note注意 the hyphen連字號 before a noun在名詞前 appears會出現（a white-tie dinner），but usually not after the verb但在動詞後通常不用（the dinner is white tie）。