nude

Posts depicting at least one character who isn't wearing any clothing at all. Not even stockings or a hat, or other non-covering clothing.

What counts as nude?

A character is allowed to wear the following items and still be considered nude:

Accessories and decorations such as glasses, collars, armbands, garters, pasties, various objects such as bags, and piercings.
Jewelry such as bracelets, rings, and necklaces.
Most forms of restraints, and bondage gear, except for suits and other covering gear that resemble normal clothing.

Nudity does not have to be erotic. This tag applies even if a character's genitals and/or nipples are not visible (such as when covered by a bed sheet or a towel, or by fur), and even when the character is drawn in a cartoonish manner and does not appear to have genitalia.

A character is not to be assumed to be wearing anything, unless it is seen. (twys) Hence a character not wearing any topwear behind a desk with their bottom not visible on the image, is to be assumed completely nude, unless there is some indication that the rest of their body would not be equally exposed. (A typical news reader on TV is wearing topwear, which gives a visible reason to assume they are wearing bottomwear too.)

Tagging for ferals

This should be tagged for feral characters only when the nudity status of the character is relevant to the context / nature of the scene, or what the character is doing.

It may be considered relevant under the following circumstances:

The character is in an intentionally provocative pose that sexualizes the character.
The context suggests that nudity for that character is not normative. If an exposure theme applies, nudity is relevant.
Characters that have more anthropomorphic traits (behave / look humanoid) and lean closer to the semi-anthro side of the feral spectrum are more relevant. If a character is depicted more like an animal, exhibiting less anthropomorphic traits, nudity is less relevant. Feral forms in general are less relevant for tags such as casual_nudity, and social_nudity without visible genitalia.
The character has visible genitalia, teats, or an anus (including x_anus).
The character is engaging in a sexual act (including feral_on_feral, and bestiality), fondling, or masturbation.
The character does not qualify as an ambient species (background character tag for ferals). Ambient species that meet any other relevant quality are a grey area and probably should be tagged nude.

A feral character wearing clothes should be tagged with clothed_feral.

Nudity is generally rated Questionable or higher, but non-sexualized cartoon (ie: characters whose standard appearance is nude, such as Bugs Bunny and others) or barbie doll nudity (ie: nude by the standards of the character(s) but having "nothing to see") can be rated Safe.

Not to be confused with

partially_clothed - open pants, unbuttoned shirts, and other partially worn clothing.
mostly_nude - when a character is almost fully naked, except for non-covering clothing such as gloves, boots, or a hat.