Lichen and Reindeer lichen

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..

Reindeer lichen and lichen are semantically related. In some cases you can use "Reindeer lichen" instead a noun "Lichen".

Reindeer lichen 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 reindeer lichen are semantically related. You can use "Lichen" instead a noun phrase "Reindeer lichen".