European Project Definitions
The CIPRNet project  uses the following definition:
Dependency is the relationship between two (critical infrastructure) products or services in which one product or service is required for the generation of the other product or service.
(Inter)dependência: relação de dependência ou interferência de uma infraestrutura crítica em outra, ou de uma área prioritária de Infraestruturas Críticas em outra. 
(Inter)dependence: dependency relationship or interference of a critical infrastructure with another, or of a Critical Infrastructure priority area with another.
IT dependency is defined as the situation where "a process depends on IT if the successful implementation of the process depends on the proper functioning of IT". 
Interdipendenza: relazione funzionale tra due sistemi o infrastrutture attraverso la quale lo stato di ogni infrastruttura è correlato allo stato dell’altra, influenzandolo ed essendone reciprocamente influenzato. 
Een koppeling tussen twee infrastructuren, waarbij het functioneren van de ene infrastructuur van invloed is op het functioneren van de andere infrastructuur. (a relationship of two infrastructures through which the functioning of one infrastructure is influenced by or is correlated to the functioning of the other infrastructure). 
The one-directional reliance of an asset, system, network, or collection thereof—within or across sectors —on an input, interaction, or other requirement from other sources in order to function properly. 
An external dependency exists when an external entity has access to, control of, ownership in, possession of, responsibility for, or defined obligations related to one or more assets or services of the organization. 
Academic definition CIPRNet
A dependency is the relationship between two critical infrastructure products or services in which one product or service is required for the generation of the other product or service. 
Academic definition United States
Dependency is a uni-directional relationship of two infrastructures through which the state of the depending infrastructure is influenced by or is correlated to the state of the other. 
- ↑ http://www.ciprnet.eu/
- ↑ GUIA DE REFERÊNCIA PARA A SEGURANÇA DAS INFRAESTRUTURAS CRÍTICAS DA INFORMAÇÃO Versão 01 (Nov. 2010).
- ↑ Unpublished working glossary of UP KRITIS and BSI, 2014
- ↑ PROTEZIONE DELLE INFRASTRUTTURE CRITICHE INFORMATIZZATE La realtà Italiana (2004)
- ↑ M.H.A. Klaver, B. Verheesen, H.A.M. Luiijf (2013). Intersectorale afhankelijkheden: buitenlandse methoden en mogelijke toepasbaarheid in Nederland, TNO 2013 R11539, The Hague, Netherlands
- ↑ National Infrastructure Protection Plan, Partnering to enhance protection and resiliency, US Department of Homeland Security, 2009
- ↑ Cyber Resilience Review (CRR): Method Description and Self-Assessment User Guide (2016)
- ↑ CIPRnet definition
- ↑ Rinaldi, S., J. Peerenboom, and T. Kelly (2001). Identifying, understanding and analysing critical infrastructure interdependencies. IEEE Control Systems Magazine, pp. 11–25.