1. 谷粒
    A grain of wheat, rice, or other cereal crop is a seed from it.

    e.g. ...a grain of wheat.
           一粒小麦
    e.g. ...rice grains.
           米粒

2. 谷物（尤指小麦或玉米）
    Grain is a cereal crop, especially wheat or corn, that has been harvested and is used for food or in trade.

    e.g. ...a bag of grain.
           一袋谷物
    e.g. ...the best grains.
           优质谷物

3. 细粒;微粒;小颗粒
    A grain of something such as sand or salt is a tiny hard piece of it.

    e.g. ...a grain of sand.
           一粒沙子

4. 一点；些微
    A grain of a quality is a very small amount of it.

    e.g. There's more than a grain of truth in that.
           其中含有很深刻的道理。

5. （木材表面的）纹理，纹路
    The grain of a piece of wood is the direction of its fibres. You can also refer to the pattern of lines on the surface of the wood as the grain.

    e.g. Brush the paint generously over the wood in the direction of the grain.
           顺着木材的纹理刷上厚厚的一层漆。

6. 违背本来的原则；与…格格不入
    If you say that an idea or action goes against the grain, you mean that it is very difficult for you to accept it or do it, because it conflicts with your previous ideas, beliefs, or principles.

    e.g. Privatisation goes against the grain of their principle of opposition to private ownership of industry.
           私有化有悖于他们反对工业私有的原则。