This question is about the time of day, just before sunrise, which in the UK is known as dawn, or morning twilight. Is there a distinction in German between the uses of "Morgengrauen" and "Morgendämmerung", or are they interchangeable? Many thanks.
Dämmerung connects with the verb (zu) dämmern which translates as (to) dim and thus is equivalent to dawn at the morning and dusk at the evening. As Germans like longer words (I am one) we connect some extra nouns to make longer words like "Morgendämmerung" = "dawn" or "Abenddämmerung" = "dusk".
The understanding is a phase where there is some light still, just not full like during the day or absent during the night. Hence the word "Dämmerung" on its own has an implicit connection to times during the day.
"Morgengrauen" (there is no real equivalent for the evening) connects with the adjective "grau" like the colour "grey". Implicit understanding means the time during the dawn where colours are not easily distinguished. Like in "In der Nacht sind alle Katzen grau." which means "All cats are alike at night." As such it is implicitly refering to the time when night ends and before morning starts.
The connection to dread ("Grauen") is more of a play with words to express an emotional state instead of a factual.
Either word describes the factual time reference of the change from night to morning, however "Morgengrauen" ends implicitly earlier than "Morgendämmerung".
The difference is in the emphasis. “Morgengrauen” is the time when the morning is still dark and gray=grau. Emphasis on bad visibility, being gray. “Morgendämmerung” is the time when the sun starts to appear and then to rise. Emphasis is on the darkness ending.
They are the same time. They are the same / different just like “glass half full” and “glass half empty” are the same or different.
The words are synonyms. However, in my opinion "Morgengrauen" has a slightly negative connotation - "Morgendämmerung" has a nicer sound. This may be a psychological effect: "Grauen" has the meaning of dawn, but also of dread.
The corresponing "Abendgrauen" seems to exist, but it is an unsual expression.