There are many different definitions but here are our favourites:
"A service is something that helps someone do something."
— Lou Downe
“When you have two coffee shops right next to each other, and each sells the exact same coffee at the exact same price, service design is what makes you walk into one and not the other.”
— 31Volts Service Design Studio
“The activity of planning and organizing people, infrastructure, communication and material components of a service in order to improve its quality and the interaction between service provider and customers. The purpose of service design methodologies is to design according to the needs of customers or participants, so that the service is user-friendly, competitive and relevant to the customers.”
— Service Design Network
The Principles of Service Design Thinking - Building Better Services