herd's grass vs Phleum pratense

herd's grass and Phleum pratense both are nouns.

Word	Noun	Adjective	Verb	Adverb
herd's grass	Yes	No	No	No
Phleum pratense	Yes	No	No	No

As nouns, herd's grass and Phleum pratense are synonyms defined as:

herd's grass and Phleum pratense: grass with long cylindrical spikes grown in northern United States and Europe for hay

Other synonyms of herd's grass include timothy.

herd's grass (noun)	Phleum pratense (noun)
grass with long cylindrical spikes grown in northern United States and Europe for hay	grass with long cylindrical spikes grown in northern United States and Europe for hay