A lodger is someone who lives with you in your home. They might be a friend or family member, but they can also be someone you don't know. Lodgers can stay with you for free or pay you rent, and sometimes pay for other services, such as meals, cleaning or laundry. Lodgers don't usually have exclusive use of a room.
Yes, this is normally allowed as long as it does not cause overcrowding or breach any restrictions that may apply at the property, such as age restriction criteria. You must also:
As the tenant, you are responsible for ensuring that the people living in your property comply with the terms of your tenancy agreement.