"朋友"的英语单词"friend"的复数形式是 加s，即"friends"。例如：

1. He has many friends.

2. They are best friends.

3. This is my friend, Tom.

4. These friends of mine are very helpful.

因此，当我们要表示多个朋友时，只需在"friend"后面加上"s"，变成"friends"即可。