masc. (+gen) stilling (of); serenity (of); calming (of); settling (of); peace (of); (comm) mental unification [√sam + a + tha] ✓
masc. (+gen) (vinaya) settlement (of); deciding (of); appeasement (of); adjudication (of) [√sam + a + tha] ✓
nt. (+gen) evenness (of); balance (of); equilibrium (of) [sama + tha] ✓
Common wrong views on samatha
⛔samatha is not equivalent to samādhi!
⛔samādhi is not "stillness"! Stillness is an essential ingredient, but Samādhi is undistractible lucidity, and one can do vipassana while in states of samādhi such as the four jhānas, and first three formless attainments. Samādhi contains both samatha and vipassana within, they operate simultaneously.
✅If you had to find the closest synonym to samatha, it wouldn't be samādhi, it would be
My preferred translation term for 'samatha'
I like 'stilling (of)' the best, because the English word 'still' contains the letters 's' and 't', and so does 'samatha'. So it helps you remember the pāḷi and english correspondence.
But in practice, I'll usually use 'serenity', because unfortunately Ajahn Brahm in modern times has popularized a (wrong) interpretation of samādhi as "stillness".
So because it's important to distinguish samādhi from samatha, I usually go with 'serenity'.