oldest or eldest

Question 1

when can you use both oldest and eldest

Answer 1

to refer to the greatest in age

Question 2

when can you only use eldest

Answer 2

to refer to people, most commonly siblings

Question 3

when can you only use oldest

Answer 3

to refer to any person, place, building

Question 4

example both eldest and oldest

Answer 4

Alex is the oldest/eldest brother

Question 5

exaple only oldest

Answer 5

Is New York the oldest city in the US