level

Compared meaning: a rank, amount, or extent of something (noun).

比较义项：等级、程度、水平（名词）。

• grade

  Grade emphasizes a formal classification of quality or performance, often on a labeled scale (A, B, C) used for school marks or product quality; less common for a general amount of something.

  grade 强调按质量或表现进行的正式分类，常用于有标签的等级（如 A、B、C），比如学校成绩或产品质量；较少用来表示笼统的“程度”。

  The eggs are sorted into grades based on their size and quality.

  这些鸡蛋按大小和质量被分成不同的等级。

• degree

  Degree highlights the extent or amount to which something is true, often in phrases like 'to a degree' or 'a degree of difficulty'; it is abstract and continuous rather than a fixed category.

  degree 强调某种性质达到的程度或分量，常见于“to a degree”“a degree of difficulty”等说法；它是抽象且连续的，而不是固定的类别。

  Success depends to a large degree on how much effort you put in.

  成功在很大程度上取决于你付出了多少努力。

• level 本词

  Level refers to a specific point or standard on a scale or hierarchy, such as skill or achievement level; it is the most general term and often replaces grade or degree loosely.

  level 指在某个尺度或层级体系中所处的具体位置或标准，例如技能水平或成就水平；它是三者中最通用的词，常可笼统地替代 grade 或 degree。

  Her fitness level improved dramatically after months of consistent training.

  经过几个月的持续训练，她的体能水平明显提高了。

Grade, degree, and level can all express a kind of rank or amount. Grade means a formal classification of quality, like a school mark. Degree means how much of a quality exists. Level, the most general term, means a point on a scale.

这三个词都可表示某种“程度”或“等级”，容易被中国学习者混用，但用法和搭配不同：grade 强调按质量或表现分类的正式等级；degree 强调某种性质达到的程度或分量；level 强调在某个尺度上所处的具体位置或标准。这里不比较 degree 的“学位”或温度单位含义，也不比较 grade 的“坡度”含义，或 level 作形容词表示“平的”的用法。

Compared meaning: smooth and without slopes or gaps (adjective).

比较义项：表面平坦、无起伏或与相邻面齐平（形容词）。

• level 本词

  Level describes a surface with no tilt, perfectly horizontal, often checked with a tool or against gravity; typically used for floors, tables, and ground.

  level 强调表面没有倾斜，完全水平，常靠工具或重力来检验，多用于地板、桌子、地面等。

  Check that the washing machine is level, or it will vibrate loudly.

  检查一下洗衣机是否放平，不然它运转时会剧烈震动。

• flat

  Flat describes a surface without bumps, curves, or slopes, evenly smooth overall, without implying it has been checked for horizontal tilt; used for land, roads, and surfaces generally.

  flat 强调表面没有凹凸、弯曲或坡度，整体平滑，不一定涉及是否水平的检验，多用于土地、道路及各种表面。

  The desert stretched out flat in every direction, without a single hill.

  沙漠向四面八方延伸得十分平坦，没有一座山丘。

• flush

  Flush describes one surface being exactly even with an adjacent surface, with no gap or step between them; it is always used in relation to another surface.

  flush 强调某一表面与相邻表面完全齐平、之间没有缝隙或高低差，总是相对另一个表面而言。

  Sand down the patch until it's flush with the rest of the wall.

  把这块补丁打磨到与墙面其余部分齐平为止。

All three describe a flat surface. Level means horizontal, with no tilt. Flat means smooth, without bumps or curves. Flush means one surface is exactly even with the surface beside it. Other senses of these words are not compared here.

这三个词都能形容“平坦”的表面，但侧重点不同：level 强调水平、无倾斜；flat 强调没有凹凸起伏；flush 强调与相邻表面对齐、齐平。这里不比较 level 的“程度、水平”义（如例句中的 advanced level）、flat 的“公寓”义（如例句中的 a small flat）以及 flush 的“脸红”义（如例句中的 begin to flush）。