A lifeline is a line or rope used to support a person who is in physical difficulty, or to prevent someone from getting into physical difficulty. For example, a lifeline may protect a person who is at risk of drowning.

Life line also refers to a line on the human palm used in chiromancy (palm reading).

Other uses

The term Lifeline may now be used metaphorically to refer to many different things which draw from this original meaning to some extent. Companies, services, and tv shows often use the term in their name.

Humanitarian / Charity

• Lifeline (Counselling service): an Australian telephone Counselling service1, also operating internationally2 (similar to CONTACT USA or the UK Samaritans)
• Lifeline is a charity in Serbia supported by Princess Katerina of The Former Republic of Yugoslavia or Serbia.
• Lifeline Radios are distributed freely in Africa and provide targeted access to information and education. The Freeplay Foundation is a non-profit humanitarian organisationLifeline Radios

Medical Services

• Philips Lifeline Medical Alert Service: In the US & Canada "Lifeline" is a private, subscription-based medical alert service provided by Philips Lifeline (a division of Royal Philips Electronics, which purchased Lifeline Systems, Inc. in 2006). Lifeline Systems was founded in 1974 by Dr. Andrew Dibner. Elderly subscribers wear medical alert devices on the wrist or around the neck, which when activated in the event of an emergency, automatically dial an emergency telephone number for assistance.3
• Community alarm units: In the United Kingdom, Lifeline refers to community alarm units, manufactured by Tunstall Group, which when linked with telecare sensors provide vulnerable people with a means of contacting help via a network of monitoring centres throughout the UK.
• LifeLine Ambulance Service operates non-emergent service to various hospitals and nursing facilities in the metropolitan Boston, Massachusetts area.4
• Lifeline Helicopter: In Indiana (USA) four LifeLine helicopters fly for medical purposes within a 150-mile radius of Indianapolis. Air medical transport reaches further.

Telephony

Some telephony devices have a "lifeline" port, powered from the central office rather than locally, so the device can still continue to work in case of power outage.

Some regulatory authorities require telephone companies to offer a minimal service for means tested customers, known as "lifeline" service.