Modifies a noun

• anaerobe: Many bacteria may however grow in both the presence or absence of oxygen, and these are termed facultative anaerobes.

• reinsurance: DMC Category Rating: C onfirmed Background The case concerned a facultative reinsurance placed with Gan Insurance Company in March 1996.

• parasite: In contrast, facultative parasites can develop in both living and dead organic matter.

• pathogen: However, the organism causes disease when changes in the skin allow it to become a " facultative pathogen " .

• endosymbionts: We are using pea aphids and their facultative endosymbionts as a model system.

• basis: GAN reinsured 2 % of this risk on a facultative basis, with Tai Ping reinsuring the remainder elsewhere.