Both older and elder describe someone or something with the higher age in a comparison. Basically, they can both be the opposite of younger. They’re similar words that are usually interchangeable. For example, let’s say a woman has two sons, one 15 years old and one 18 years old. She could describe the 18-year-old boy as her older son or her elder son, and the meaning would be the same.
Unlike older, elder can also function as a noun. For example, senior citizens are often called elders, even when they aren’t being directly compared to a younger group of people.
Usage in Comparisons
Older is only ever used as a comparative term. When you say something is older than something else, it doesn’t necessarily mean that the thing is objectively old. For example, you might say a shirt that you bought two months ago is older than a shirt you bought today. Both shirts are still relatively new, but in this case the first one is older than the second.
Elder can refer specifically to a person who’s objectively old. So it’s more useful in instances when where no particular comparison is being made.
Elder as a Noun
The word elder also tends to be used as a noun to describe seniors. As a noun, elder means an aged person. This is distinct from the older party in a comparison. An elder is objectively older than the majority of the population.
Different Uses of Elder
Elder can describe a person who has authority based on age and experience. It can also be used as a term to describe specific rank. In some cultures, religions, and literature, elders are figures of high ranking and social influence. Bear in mind, though, a person who is an elder isn’t necessarily old. For example, in the Mormon church, a member of the Melchizedek priesthood is referred to as an elder, regardless of age.
The word elder can also function as a chronological marker. In J. R. R. Tolkien’s The Lord of the Rings series, the earliest recorded age of Middle Earth is described as the “Elder Days.” It’s a moniker which makes sense because it was the oldest historic age. In the first novel of the trilogy, The Fellowship of the Ring, Tolkien writes that Frodo feels “that he had stepped over a bridge of time into a corner of the Elder Days, and was now walking in a world that was no more.”