What is the difference between a reasonable modification and a reasonable accommodation?

A reasonable modification is a physical change to a dwelling or common area that a tenant with a disability is permitted to make at their own expense, such as installing grab bars, widening doorways, or building a ramp. A reasonable accommodation is a change in rules, policies, practices, or services that allows a person with a disability equal opportunity to use and enjoy their housing, such as waiving a no-pets policy for a service animal or providing a reserved parking space near the entrance. Landlords must allow both unless they would impose an undue financial or administrative burden.