We provide evidence that the symbiosis of fungal endophyte and plant host \nshould only be defined in the broad sense as originally used by De Bary to mean the \nliving together of organisms of different species. Using endophytic fungi that were \nisolated from healthy plant tissue,- we tested for the potential pathogenicity of the \nfungal isolates and did physiological experiments to understand the endophyte-host \nassociation. Due to the variability of the interaction with respect to the role of the \nendophyte and with respect to the physiological Status of both partners, only a \ndefinition of symbiosis that does not specify the advantages and disadvantages for \nthe individual partners can accurately describe this interaction.