layby vs lay-by

layby and lay-by both are nouns.

Word	Noun	Adjective	Verb	Adverb
layby	Yes	No	No	No
lay-by	Yes	No	No	No

As nouns, layby and lay-by are synonyms defined as:

layby and lay-by: designated paved area beside a main road where cars can stop temporarily

Other synonyms of layby include pull-off, rest area, rest stop.

layby (noun)	lay-by (noun)
designated paved area beside a main road where cars can stop temporarily	designated paved area beside a main road where cars can stop temporarily