n.

1. 迁移；（候鸟等的）迁徙[U][C]
   There has been a migration of people from the country to the towns.

   人们从乡下移居城镇。

   the annual migration of birds

   候鸟每年的迁徙

2. 移民群；移栖动物群[C]
   Ornithologists like to study the migration of birds.

   鸟类学家喜欢研究鸟的移栖动物群的行为。

3. 【化】【物】移动，徙动