Macrencephalic refers to organisms, including humans, who have a larger brain size relative to their body size than other organisms. There are a few synonyms for this term that can be used in place of macrencephalic, including megalencephalic, megacephalic, and large-brained. Megalencephalic and megacephalic both come from the prefix "mega," meaning large, while "cephalic" refers to the head. Large-brained is a more straightforward synonym, simply referring to the larger size of the brain. These terms can be useful when discussing evolutionary or genetic differences in brain size among species, or when describing individuals with certain neurological conditions such as autism.