May I have a word with you?

当你有重要事要打断别人的谈话或工作，最好先礼貌地问句：May I have a word with you?　（我可以和你谈一会吗？）。虽然是a word，但不是只说一个字而已，而是一段很简短的对话，或可以说：May I have a quick word with you? / May I have a word in your ear? 通常有这样的要求，谈话内容可能比较私人或秘密，或者也可以用A word if you don't mind.（只是一句话，如你不介意）。
对话
A: Julie, may I have a word with you, please?
B: Sorry, I'm a bit tied up at the moment. Can we talk later?
A: You said that earlier and I've been waiting all afternoon. I only need 5 minutes to go over this.
B: , please take a seat.
甲：茱莉，我可否和你谈一会吗？
乙：对不起，我现在很忙，可否迟些再谈？
甲：你较早前已这样说过，而我已等了整个下午，我只需要5分钟就足够了。
乙：好吧，请坐。

May I have a word with you?即‘我可否和你谈谈吗？’A word两字可不可以改作words? 改作words，意思就完全不同了。To have a word with somebody. 是‘和某人谈谈’，To have words with somebody. 则是‘和某人吵架’，例如：He had words with his wife last night. (他昨晚和妻子吵架）。

又请看以下两句有什么分别：He had white hair、He had white hairs。 按hair泛指毛发，是不可数名词，例如：I find her shoulder-length hair very beautiful.（我觉得她及肩的头发很美丽）。但是，一根毛发却是可数名词（countable noun），例如成语to hang by a hair即‘系于一发’，His life is hanging by a hair. 等于‘他生死悬于一发’。He had white hair.是说‘他满头白发’，He had white hairs.则是说‘他头上有些白发’。