The closest in canon is sil, 'soul', a strictly immaterial word. The closest non-canon is hil, a word that (unfortunately) shares all the usages and connotations of its English equivalent. If pure canon is required together with a precise equivalence, you can do as some poems do and make a descriptive 'crutch' compound by combining one of these descriptors

sos- 'blood'
laas- 'life'
kosil- 'inner'

with one of these nouns

-tu 'hammer'
-nos 'strike'
-yoriik 'march'