Question

she sat down (down word was what type of part of speech)​

Answer 1

Explanation:

down is a noun

sat is verb

she is subject

Answer 2

it is a preposition,

As a preposition, down can be used in informal British English without 'to' or 'at' when talking about a place that is near you, e.g. 'He's down the pub with his mates'. As an adverb, down can mean 'going towards the south', as in 'Thousands of Scottish fans will be travelling down to London for the big match'.