A mutually beneficial relationship where one organism lives inside the cells of another, like how mitochondria came to live inside our cells.
From endo- (Greek 'within') + symbiosis (Greek sym 'together' + bios 'life'). Proposed by Lynn Margulis in the 1960s-70s, revolutionizing evolutionary biology.
Your cells contain tiny power plants called mitochondria that were once free-living bacteria—they got swallowed by ancient cells and decided to stay, making complex life on Earth possible!
Complete word intelligence in one call. Free tier — 50 lookups/day.