1) FIAP Definition:
A black and white work fitting from the very dark grey (black) to the very clear grey (white) is a monochrome work with the various shades of grey. A black and white work toned entirely in a single color will remain a monochrome work able to stand in the black and white category; such a work can be reproduced in black and white in the catalogue of a salon under FIAP Patronage.
On the other hand a black and white work modified by a partial toning or by the addition of one color becomes a color work (polychrome) to stand in the color category; such a work requires colour reproduction in the catalogue of a salon under FIAP Patronage.

2) PSA Definition:
An image is considered to be Monochrome only if it gives the impression of having no color (i.e. contains only shades of gray which can include pure black and pure white) OR it gives the impression of being a greyscale image that has been toned in one color across the entire image. (For example by Sepia, red, gold, etc.) A greyscale or multi-colored image modified or giving the impression of having been modified by partial toning, multi-toning or by the inclusion of spot coloring does not meet the definition of monochrome and shall be classified as a Color Work.

Nature Definition (FIAP & PSA):

Nature photography is restricted to the use of the photographic process to depict all branches of natural history, except anthropology and archeology, in such a fashion that a well-informed person will be able to identify the subject material and certify its honest presentation.
• The story telling value of a photograph must be weighed more than the pictorial quality while maintaining high technical quality.
• Human elements shall not be present, except where those human elements are integral parts of the nature story such as nature subjects, like barn owls or storks, adapted to an environment modified by humans, or where those human elements are in situations depicting natural forces, like hurricanes or tidal waves.
• Scientific bands, scientific tags or radio collars on wild animals are permissible.
• Photographs of human created hybrid plants, cultivated plants, feral animals, domestic animals, or mounted specimens are ineligible, as is any form of manipulation that alters the truth of the photographic statement.
• No techniques that add, relocate, replace, or remove pictorial elements except by cropping are permitted.
• Techniques that enhance the presentation of the photograph without changing the nature story or the pictorial content, or without altering the content of the original scene, are permitted including HDR, focus stacking and dodging/burning.
• Techniques that remove elements added by the camera, such as dust spots, digital noise, and film scratches, are allowed.
• Stitched images are not permitted.
• All images must appear natural.
• Color images can be converted to greyscale monochrome.
• Infrared images, either direct-captures or derivations, are not allowed.
• Images entered in Nature sections meeting the Nature Photography Definition above can have landscapes, geologic formations, weather phenomena, and extant organisms as the primary subject matter. This includes images taken with subjects in controlled conditions, such as zoos, game farms, botanical gardens, aquariums and any enclosure where the subjects are totally dependent on man for food.

Photo Travel Definition (PSA):

By the sole act of submitting his/her images or files to a salon under FIAP Patronage, the entrant accepts without exception and with no objection that the submitted images can be investigated by FIAP to establish if these obey to FIAP regulations and definitions even if the entrant is not a member of FIAP; that FIAP will use any means at its disposal for this undertaking; that any refusal to cooperate with FIAP or any refusal to submit the original files as captured by the camera, or failure to provide sufficient evidence, will be sanctioned by FIAP and that in case of sanctions following the non compliance with FIAP regulations, the name of the entrant will be released in any form useful to inform the breaches of the rules. It is recommended to leave the EXIF data in the submitted files intact in order to ease eventual investigations. The PSA has provisions similar to those described above.