reachable

It then traverses the chain of references until all (directly or indirectly) reachable objects from the root set are marked.

跟踪然后遍历引用链直至标记完根集中所有（直接或间接）可获得的对象。

To make life easier (and it is good practice anyway), we make sure that all data is reachable from the root of a single tree of data structures in memory.

为了让生活更容易（它总是一个很好的实践），我们必须确保所有的数据从单一数据结构书的根上是可获得的。