I am learning about the marker genes and clustering by Seurat in scRNA-seq datasets. However, I am confused about the term positive marker and negative marker. What I understand is the marker genes of a cluster is the genes which are highly expressed (high counts) in the cells of that cluster. Let's say cluster A has 200 genes. My questions are:
Can I say that those 200 genes are marker genes for cluster A? How to determine which marker genes are positive marker genes and which are negative marker genes?