Arctic moss and Lichen

Arctic moss noun - An erect greyish branching lichen of Arctic and even some north temperate regions constituting the chief food for reindeer and caribou and sometimes being eaten by humans.

Lichen and arctic moss are semantically related. In some cases you can use "Lichen" instead a noun phrase "Arctic moss".

Lichen noun - Any thallophytic plant of the division Lichenes; occur as crusty patches or bushy growths on tree trunks or rocks or bare ground etc..

Arctic moss and lichen are semantically related. Sometimes you can replace phrase "Arctic moss" with "Lichen", this terms are similar.