Hetair- or latinicized Hetaer- is a Greek linguistic root bearing the meaning of companion (cf. Latin Socii and societas). It is used in the following terms:

• Hetairoi (sing. Hetairos), the name of the Macedonian aristocracy and later Companion cavalry
• Hetaira (plural Hetairai), female sophisticated companions, courtesans
• Hetairideia, a festival of Magnesians and Macedonians
• Hetairiai or Ancient Greek clubs, associations of ancient Greeks who were united by a common interest or goal
• Hetairia or Andreia, the Cretan terms for Doric Syssitia (common meals)
• Hetaireios, an epithet of Zeus

• Filiki Eteria, a secret 19th century organization whose purpose was to overthrow Ottoman rule over Greece and to establish an independent Greek state
• The Greek term for company, found in many business names such as Jumbo Anonymi Etairia

• Hetaeria, or hairy jewel orchids, a genus in the family Orchidaceae
• Hetaerina: a genus of damselfly
• Hetaira (katydid): a genus of bush crickets

• Hetaireia, a Byzantine imperial guard
• Hetaerism, a theoretical early state of human society that practiced a polyamorous and communistic lifestyle; see Matriarchal religion