Classification of aircraft Generation

Hi guys,

I’m confusing :confused:about I discussed the Aircraft generation issue with my friend few days ago, I found that F-15 and F-16 falcon are the 4th Gen (info from WIKI) , but my friend persist in his point said F-15 and F-16 are 3 or 3.5 Gen in US air force standard, really don’t know what info source he base on, I knew that Western and Russian have different standards, I just wanna know the true classification standard of USAF, anybody knows? Would you pls tell me am I wrong?:confused:

Best regards,