Apeiron (/əˈpaɪˌrɒn/;[1] ἄπειρον) is a Greek word meaning '(that which is) unlimited; boundless; infinite; indefinite'[2] from ἀ- a- 'without' and πεῖραρ peirar 'end, limit; boundary',[3] the Ionic Greek form of πέρας peras 'end, limit, boundary'.[4]