@How to use zatR bases

The old grammarians and commentators do not bother to explain how you should use a -zatR- word in a sentence, because they just assume that you speak fluent sanskrit and you already know how to do that.

So a little explanation might help up to clarify things.

A word like pacan पचन् means "that is / was cooking" and it is a masculine noun with first ending. It comes from the present verb pacati पचति "cooks". To be precise, pacan पचन् is pac पच् + /laT, then laT लट् is replaced by /zatR, forming a nounbase "pacatR", and then /su is added after the nounbase.

The pacan पचन् word must always linkto some other noun in some full sentence. It cannot form a sentence by itself, usually. So starting with a sentence like:

rAjA kapim apazyat राजा कपिमपश्यत् "king saw monkey"

...we can link pacan पचन् to rAjA राजा because rAjA राजा has same gender, same number, same case. The resulting sentence will mean "king was cooking and king saw monkey" or "king, while cooking, saw monkey" or just "cooking king saw monkey" or maybe "the king who was cooking saw the monkey". That sentence mighht be:

pacan rAjA kapim apazyat पचन्राजा कपिमपश्यत् "cooking king saw monkey"

But the pacan पचन् word can be placed anywhere.