Noun-forming suffix — “state or condition of,” “abnormal or diseased process,” “pathological change”
The suffix entered English in the 1500s as part of phthisis and leucosis (noun), borrowed from Latin -osis, from Greek -ωσις (-ōsis) — literally “a state or condition.” The term cirrhosis appeared in the 1820s, and neurosis in the 1820s. The suffix -ōsis (“condition, state”) connects -osis to the entire condition and state suffixes: cirrhosis (kirros + -osis → condition of hardening/fibrosis), neurosis (neuron + -osis → abnormal condition of the nerves), and leukosis (leukos + -osis → white blood cell disorder). The noun-forming suffix-osis is extremely productive across nearly all medical specialties: e.g., arthritis (cf. -itis), fibrosis, cirrhosis, leukosis, neurosis, and osteosclerosis (cf. -osis variant).