If your router assigns DHCP addresses in a certain range and assuming no human has also assigned addresses in that range, (they shouldn't) then any address in that range is a DHCP address
example your router is 192.168.1.1 and it hands out 100 addresses starting at 192.168.1.100
any address below 100 or over 200 is manually set, and (assuming humans who know not to hard code in the DHCP range)any address within 100 to 200 is DHCP
I tried to remain child-like, all I acheived was childish.