Principles - 原则
Material design is guided by print-based design elements – such as typography, grids, space, scale, color, and imagery – to create hierarchy, meaning, and focus that immerse the user in the experience. Material design adopts tools from the field of print design, like baseline grids and structural templates, encouraging consistency across environments by repeating visual elements, structural grids, and spacing across platforms and screen sizes. These layouts scale to fit any screen size, which simplifies the process of creating scalable apps.
【翻译】
材料设计由基于打印的设计元素（例如排版，网格，空间，比例，颜色和图像）指导，以创建将用户沉浸在体验中的层次结构，含义和焦点。 材料设计采用来自打印设计领域的工具，如基准网格和结构模板，通过重复视觉元素，结构网格以及跨平台和屏幕尺寸的间距，鼓励跨环境的一致性。 这些布局适合任何屏幕大小，这简化了创建可扩展应用程序的过程。
How paper works
In material design, the physical properties of paper are translated to the screen. The background of an application resembles the flat, opaque texture of a sheet of paper, and an application’s behavior mimics paper’s ability to be re-sized, shuffled, and bound together in multiple sheets.
The surfaces that comprise applications are referred to in this spec as material, or sheets of material.
Elements outside of applications, such as system bars, are separate from the app content beneath them, and are not treated as material.
For detailed information about material, see Material Properties.
【翻译】
在material design中，纸的物理性质被转化到屏幕上。 应用程序的背景类似于一张纸的平坦，不透明的纹理，应用程序的行为模仿了纸张在多个页面中重新调整大小，混排和绑定的能力。 包括应用的表面在本规范中被称为材料或材料片。 应用程序之外的元素（例如系统栏）与其下的应用内容是分开的，不会被视为材料。 有关材质的详细信息，请参阅材料属性。
Seams - 接缝
Two sheets of material that share an entire common edge are called seams. While joined by a seam, they move together.
【翻译】
共享整个公共边缘的两张材料称为接缝。当通过接缝连接时，它们一起移动。
Seams in two sheets of material
【翻译】
两张材料中的接缝
Steps - 层阶
Two overlapping sheets of material, with different z-positions (or depths), form a step. They move independently of each other.
【翻译】
两个重叠的材料片，具有不同的z位置（或深度），形成一个台阶。它们彼此独立移动。
Steps in two sheets of overlapping material
【翻译】
在两张重叠材料中的层阶
Floating action button - 浮动按钮
A floating action**** button is a circular sheet separate from a toolbar. It represents a single promoted action.
It can straddle a step if it relates to the content creating that step.
【翻译】
浮动操作代表在当前情境下的独立提升操作。当与产生这个层阶[step]的页面内容相关联时，它可以跨越这个层阶。
Floating action buttons straddling steps
【翻译】
浮动动作按钮跨越层级
A floating action button can straddle a seam if it relates to the content of both sheets.
【翻译】
浮动操作在与产生这个叠合线的两个页面内容相关联时，可以跨越这个缝合线。
Do not introduce a decorative seam to provide an anchoring point for an action.
【翻译】
永远不要仅仅为了给操作提供一个支撑点而引入一条装饰性的缝合线。