For some reason unknown to me and ,as far as I know, unexplained, it only changes the past tense.
So, in Welsh , verbs like nabod, meddwl, credu, ofni, poeni and perthyn are considered to be "not active" and don't generally take the preterite .. instead they do this ... I've borrowed Mr. King's examples....
Oedd y gar 'ma'n perthyn i'w deulu am flynyddoedd lawer. ( it was belonging)
O'n i'n meddwl byddai rhaid aros tan y Gwanwyn. ( I was thinking)
And as the esteemed Mr. King also points out, this difference is not always adhered to.
My big question is, surely there are lots of other verbs that are inactive mental states.. teimlo, cynllinio, dwlu, sylweddoli, edmygu, penderfynu, parchu, trachwantu for example ...are these included? Who draws the line? Is there a line? And if there is, is it a straight line? What colour is it ?
That's enough worrying and fearing and thinking for now .... music beckons with its subtle charms .....