These words overlap, but they draw attention to different details: available space, contents, tightness, or something going beyond a limit.
- Full means something has reached its capacity. The hotel is full tonight. There are no rooms available. The word does not necessarily suggest discomfort or tight packing.
- Filled describes something that has had contents put into it, often using with: The basket was filled with apples. It draws attention to the contents or the action. It does not always mean completely full: She filled the glass halfway with juice.
- Packed means very full of people or things, usually close together. The stadium was packed with fans. This is stronger than simply saying there were many people.
- Crowded usually describes a place with many people and limited space. The market gets crowded at lunchtime. It need not be completely full, but moving around may be difficult.
- Crammed suggests people or things squeezed into a space that is too small. Five adults were crammed into the tiny kitchen. It emphasizes tightness, often with discomfort or too little room.
- Overflowing literally means contents are spilling over the edge. The sink was overflowing. It goes beyond being full: the contents are no longer staying inside.
A train can be crowded without reaching capacity. Calling it packed emphasizes how full it is; saying passengers are crammed inside emphasizes how tightly they are squeezed together.