Prefix used in compounds to express something that is always the same, permanent, or unchanging. Common in words like 常夏 (eternal summer) and 常春 (eternal spring).
This island is a paradise of eternal summer.
There are regions where an eternal spring climate continues.
everlasting summer; eternal summer
eternity; permanence; forever
everlasting darkness; eternal night
eternalness; forever unchanging · distant land over the sea; world of the dead
perpetual night; eternal darkness · continuing all night; all-night
The prefix 常 (とこ) is derived from the classical Japanese adjective 常し (とこし) meaning 'eternal' or 'unchanging'. It is related to the more common word 常に (つねに, 'always').