endlessness
Word family
Synonym discussion
Sense: noun/1
All four words describe something without a clear end, but they differ in context and register. 'Endlessness' is the most general and everyday word, used for situations or feelings that seem to go on forever (the endlessness of a boring meeting). 'Infinity' is more technical and mathematical, describing an actual unbounded quantity or space. 'Perpetuity' is formal and appears mainly in legal or financial phrases ('in perpetuity'). 'Eternity' carries a spiritual or religious tone, referring to timeless existence after death or a sense of permanence outside of time. In casual use, 'endlessness' is the best choice for physical or emotional experiences; 'eternity' works for dramatic exaggeration ('this queue is taking an eternity').
Etymology
Formed in English from the adjective 'endless' (Old English 'endelēas', meaning 'without end') plus the noun suffix '-ness', which turns adjectives into nouns expressing a state or quality. The word has been used since at least the 16th century.