Seder vs supper

Seder and supper both are nouns.

Word	Noun	Adjective	Verb	Adverb
Seder	Yes	No	No	No
supper	Yes	No	No	No

As nouns, supper is a hypernym of Seder; that is, supper is a word with a broader meaning than Seder:

Seder: (Judaism) the ceremonial dinner on the first night (or both nights) of Passover
supper: a light evening meal; served in early evening if dinner is at midday or served late in the evening at bedtime

Seder (noun)	supper (noun)
(Judaism) the ceremonial dinner on the first night (or both nights) of Passover	a light evening meal; served in early evening if dinner is at midday or served late in the evening at bedtime
	a social gathering where a light evening meal is served