乐是指人们在生活中感受到的快乐、愉悦、满足的情绪状态。它可以来源于不同的事物，如音乐、游戏、运动、社交等，也可以是内心的一种感受。乐常常与幸福和满意在一起，是人们追求的目标之一。

How to read: lè [lə]

Usage: 乐可以用作名词和形容词。作为名词时，它表示快乐和愉悦的情绪；作为形容词时，它表示令人愉悦的。

Example sentences:

1. She always finds joy and happiness in the little things, and that's what makes her truly happy. 她总是能从小事中找到快乐和幸福，这才是使她真正快乐的原因。

2. The children's laughter filled the air with joy and their parents couldn't help but smile. 孩子们欢笑声充满了空气，他们的父母也忍不住笑了起来。

3. Playing with my dog always brings me so much joy and relaxation after a long day at work. 和我的狗玩耍总能给我带来那么多欢乐和放松，在工作了一整天后特别有效。

4. The concert was a feast for the ears, and everyone in the audience was filled with joy and happiness. 音乐会是一场耳目一新的盛宴，所有观众都充满了欢乐和幸福。

5. His cheerful personality and positive attitude always bring joy and light to those around him. 他开朗的个性和积极的态度总能给周围的人带来欢乐和光明。

Synonyms and usage:

1. 快乐 (kuài lè) - happiness, joy; can be used interchangeably with 乐 in most cases.

2. 愉悦 (yú yuè) - pleasure, delight; often used to describe a more subtle or peaceful form of joy.

3. 幸福 (xìng fú) - happiness, bliss; refers to a long-term state of contentment and satisfaction.

4. 满意 (mǎn yì) - satisfaction, contentment; can be used to describe a feeling of joy or happiness with a specific situation or outcome.

5. 欢快 (huān kuài) - cheerful, lively; describes a feeling of joy that is accompanied by high energy and liveliness.

Editor's summary:

乐是一种人们追求的情绪状态，可以来源于不同事物。它可以用作名词和形容词，常与幸福和满意在一起。同义词有快乐、愉悦、幸福、满意等，但每个词都有其特定的用法和含义。无论是从小事中找到快乐，还是享受音乐会带来的欢乐，乐都是人们生活中不可或缺的一部分。