Questions & Answers about Bíllinn er rauður.
Icelandic typically follows Subject–Verb–Predicate (S–V–P) order. Here:
• Subject: Bíllinn (“the car”)
• Verb: er (“is”)
• Predicate adjective: rauður (“red”)
There is no separate indefinite article (“a”/“an”) in Icelandic. For an indefinite meaning you simply use the noun in its base (indefinite) form:
Bíll er rauður (“A car is red”).
You change to plural definite forms:
• bíll → bílarnir (–ar for masculine plural, –nir for the definite suffix)
• er → eru (plural of the copula)
• rauður → rauðir (masculine nominative plural)
So you get: Bílarnir eru rauðir.
When an adjective directly modifies a noun, it precedes the noun and is declined according to gender, number, and case (indefinite):
rauður bíll (masculine, singular, nominative indefinite) = “a red car.”