indeclinable (sandhi contraction of tathā + eva)
Analysis. tathā (adverb, 'thus, so') + eva (particle, 'just, only, even') — the contraction emphasizes the manner or identity of what precedes: 'in exactly that way', 'just as it is'.
Etymology. tathā is an old adverbial form from the root √tā 'stretch, extend' (seen in Sanskrit tāti 'stretches'), originally concrete imagery of laying things out flat or in a line, hence 'arranged in order' and then 'accordingly, thus'. The suffix -eva (from √vi 'to separate, distinguish') intensifies or isolates: 'just this one way, nothing else'. No direct English cognate, but compare Latin talis 'such' from the same Indo-European base.
Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.
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