to become part of a group, country, society, etc., or to make someone or something become part of a group, country, society, etc.

The European Union should remain flexible enough to assimilate more countries quickly. 欧盟应该保持足够的灵活性，以加快步伐吸收更多的国家为其成员。

You shouldn't expect immigrants to assimilate into an alien culture immediately. 你不应该指望移民能够马上融入一种外国文化中。

to understand and remember new information and make it part of your basic knowledge so that you can use it as your own

It's hard to assimilate so much information. 很难吸收这么多的信息。

to absorb food or a substance into the tissue of a living organism

In this form vitamins can be easily assimilated by the body. 在这种形态下，维生素非常易于身体吸收。