goodevening 是晚上好的意思，而good afternoon则是下午好的意思，区别可以从以下例子看出：I met my friend after lunch, so I say good afternoon to him, have chat.Then back to work, When I arrived home It was dark, saw him again, have to say good evening, then come home. 午饭后我遇到了我的朋友，所以我和他说下午好，聊聊天。

然后回去上班，到家的时候天黑了，又看到他了，不得不说晚上好，然后回家了。