推荐回答（3个）
1、定义不同
ul 是 Unordered List（无序列表）的缩写。
标签定义列表项目（li是lists的缩写）。
2、用法不同
标签定义无序列表。使用 - 标签定义的列表可以是个无序列表也可以是有序列表。
3、支持的HTML全局属性不同
- 标签支持所有的HTML 全局属性。
标签支持 HTML 中的全局属性：accesskey、class、dir、id、lang、style、tabindex、title。
4、属性不同
当时学的时候也很头疼 你是不是觉得不好控制他的浮动呀？
个人见解：（印证是对的哦）
1.ul li标签 是一对无序清单列表，见过新闻列表吧！就是那个！
2.放在div中是为了做成一个容器用的 当然你也可以用别的容器标签比如span等！但是用ul li 是因为他是一个列表标签 其次控制他的css样式是比较方便的！
3.关于ul li浮动问题 你可以让li 整体浮动 然后清空浮动 可以把li想像成一个个小方块 ul就是装这些小方块的 大箱子 控制li 不能超出ul这个箱子规定的范围
4.有些标签用多了 用熟了自然就明白了 如果看了我的解释还是不明白，你可以把这个质疑先放放 先做先用 等熟练了 再回头看看你会豁然开朗
5.希望能帮到你
li是不能单独使用，必须在于ul之中的。
ul是块级元素，能直接定义宽高，而li是行级元素，不能直接定义 高。
3个 li 只能写在ul之中，直接定义li的宽高是无效的，必须先转换为块级元素。
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