Assertion: nautical twilight | /r/Synonym | nightfall
Facets:
value: sometimes
type: TEMPORAL
value: at night
type: TEMPORAL
Source sentences:
text: It is probably telling that it is morning nautical twilight that is known as "first light" and evening nautical twilight that is called "nightfall", as that is when it gets truly obviously light or dark for the lay observer.
text: At night, nautical twilight is sometimes called “nightfall,” referencing the fact that the sky is rapidly starting to darken, and it is soon going to be so dark that artificial light will be a necessity.