mutual
/ˈmjuːtʃuəl/·뮤추얼·adjective
shared between two or more parties; reciprocal
LatinCEFR B2
Root
Latin 'mutuus' (reciprocal, borrowed), from 'mutare' (to change)
Latin mutuus (exchanged, reciprocal) → Old French mutuel → English mutual (15th c.)
In a word
Latin mutuus = 'reciprocal, borrowed back and forth'. The adjective branch of mutare (to change). Within the mut family, mutual is 'change' made two-sided — mutual (changing places = reciprocal), mutuality (reciprocity), mutate (to change), commute (to exchange = to travel daily). A "mutual fund" is one where investors literally share — exchange — capital. The Latin root, still operating.
Examples
They had mutual respect.
It was a mutual decision.
They share a mutual friend.
Related
mutuallymutualitymutual fundmutatecommute