.osm parsing: nodes that are not part of a way?!

Helle everyone,

parsing a .osm-file (part of hannover) i saved all nodes in a list and all ways with their node-ids in another.
Comparing this two list shows me, that i have 20324 nodes but only 19009 of them are part of a way. Is this a realistic number of points that are not part of any way or is there maybe a mistake in my parsing-algorithm?

Greetings from hannover