Iff

An integer is natural iff it is greater than or equal to 0.

A rectangle is a square iff all four of its sides have the same length.

For iff the patient be aſhamed to diſcloſe hiſ wounde to the phyſician which knoweth it not , phyſicke can not helpe him.

Another red alert last night. Lasted only five minutes, Possibly just a friendly plane with its IFF turned off.

IFF confirmed. Contact is Pelican Dropship Kilo 23. Over.