?dull一詞可以作為形容詞或動詞使用，其意思為“無聊的、遲鈍的”或“使變得無聊、變得遲鈍”。下面將分別介紹其用法和例句。

一、dull作形容詞時，常用來形容人或物的狀態，表示缺乏興趣、活力或刺激，單調乏味。

1. His speech was so dull that I almost fell asleep.

他的演講太無聊了，我差點睡著了。

2. The movie was really dull, I regretted buying the ticket.

這部電影真是太無聊了，我后悔買票了。

3. The students were bored by the dull lesson.

學生們被枯燥的課程搞得厭煩。

4. She has a dull personality and rarely smiles.

她性格沉悶，很少笑。

5. The party was a bit dull, there was not much to do.

這次聚會有點無聊，沒什么事可做。

二、dull作動詞時，常用來表示使某物變得無聊或遲鈍。它也可以指減弱光線、聲音等的強度。

1. Reading this book always dulls my senses.

看這本書總是讓我的感覺變遲鈍。

2. He tried to liven up the conversation but his jokes just dulled it even more.

他試圖活躍談話，但他的笑話只是讓氣氛變得更加沉悶。

3. The music was so loud that it dulled my hearing for a while.

音樂聲太大，讓我聽力一時變得遲鈍。

4. The constant rain dulled the colors of the landscape.

持續的雨水使得景色變得暗淡。

5. The medication dulls the pain, but it doesn't cure it.

這種藥物可以減輕疼痛，但不能治愈它。

總的來說，dull一詞常用來形容缺乏興趣、活力或刺激，也可以表示使某物變得無聊或遲鈍。它的反義詞為exciting（令人興奮的）或sharp（敏銳的）。在寫作中，我們也可以使用一些同義詞來避免重復使用dull，比如boring（無聊的）、tedious（枯燥的）、monotonous（單調乏味的）等。

參考例句：

1. After a long and dull day at work, I just want to relax and do nothing.

工作了一整天后，我只想放松休息。

2. The speaker's voice was so dull that I couldn't concentrate on what he was saying.

演講者的聲音太沉悶了，我無法集中注意力聽他在說什么。

3. The class was so dull that half of the students fell asleep.

這節課太無聊了，一半的學生都睡著了。

4. The city's nightlife is quite dull compared to other places I've been to.

和我去過的其他地方相比，這個城市的夜生活很無聊。

5. The teacher tried to make the lesson more interesting, but it was still dull and unengaging.

老師試圖讓課程更有趣，但它仍然枯燥乏味，缺乏吸引力。