• ossicone
• penis_horn - A penis taking the place of a horn. Probably shouldn't be tagged as horn unless there is a visible horn structure.
• unicorn_horn - A single horn centered on the head. It tends to be straight with a pointed tip. Some unicorn horns have a twisting spiral shape.
• unusual_horn

By Location

• head_horn
• nose_horn

• black_horn
• blue_horn
• brown_horn
• green_horn
• grey_horn
• maroon_horn
• orange_horn
• pink_horn
• purple_horn
• red_horn
• tan_horn
• white_horn
• yellow_horn

• monotone_horn - only one distinct color.
• two_tone_horn - only two distinct colors.
• multi_tone_horn - more than two distinct colors.
• multicolored_horn - at least two distinct colors.
• rainbow_horn

• dark_horn - Dark colored
• light_horn - Light colored

Texturing and Appearance

• dipstick_horn
• glistening_horn
• glowing_horn
• ridged_horn
• smooth_horn
• spotted_horn
• striped_horn
• translucent_horn
• wooden_horn

• bodily_fluids_on_horn
• blood_on_horn
• cum_on_horn
• pussy_juice_on_horn
• saliva_on_horn
• sweat_on_horn
• urine_on_horn
• feces_on_horn
• vomit_on_horn

Form and Shape

Horn shaft

• broken_horn
• curved_horn
• curled_horn
• wavy_horn
• forked_horn
• long_horn
• short_horn
• spiral_horn - Not to be confused with ridged_horn or curled_horn.
• straight_horn

Horn tip

• blunted_horn
• rounded_horn
• sharp_horn

• 1_horn
• 2_horns
• multi_horn - Three or more horns on a single character.
• 3_horns, 4_horns, 5_horns, 6_horns, 7_horns, 8_horns, 9_horns, 10_horns

• horn_accessory
• horn_bell
• horn_bow
• horn_jewelry
• horn_ring
• horn_ornament
• horn_piercing
• horn_ribbon
• horn_wraps
• horn_bondage
• horn_clothing

• holding_horn
• horn_grab
• horn_fetish
• horngasm
• horn_play
• horn_lick
• horn_sex
• hornjob
• horn_masturbation
• horn_penetration
• horn_in_ass
• horn_in_cloaca
• horn_in_mouth - May not be considered penetration.
• horn_bite
• horn_suck
• horn_in_pussy
• horn_in_urethra
• horn_in_penis
• horn_vore
• after_horn_play
• after_horn_sex
• after_hornjob
• after_horn_masturbation
• after_horn_penetration
• horn_transformation
• horn_expansion
• horn_growth

• horn_magic
• this_isn't_my_horn

Besides fantastical creatures such as dragons, unicorns and demons, horns (and antlers and ossicones) are overwhelmingly associated with ruminants, of which 6 families currently exist.

Ossicones are only present in giraffids, specifically the male okapi and all giraffes. They're already born with tiny, vascularized ossicones, albeit they're soft and dettached from the cranium so as to not affect birth. Within few weeks, they attach, harden and grow, but result in relatively short, straight protuberances covered by skin and fur. Some extinct giraffids produced long and/or branched structures. In some populations, males tend to develop a third horn, between its eyes, after reaching maturity. Rarely, a male giraffe may be born with a second pair of ossicones, immediately behind the first.

Antlers are the telltale feature of cervids, a.k.a. true deers. They sprout straight from the cranium in male, juvenile individuals, remaining covered in skin and sparse fur ("velvet"), which slough off once the antlers are fully grown, exposing the typically large, branched bone. This also incurs further hardening and the atrophy of the blood vessels within. However, the hard antlers are shed every year, and regrown anew for the rest of the animal's life. Females rarely present antlers, which is, usually, a sign of hormonal imbalance. The sole exception to that are reindeers, in which all females have them, altho typically smaller than those of males.

True horns, as mentioned above, refers to bony protrusions and their covering made of keratin, of which the word horn also is a synonym. These are sported by all wild male specimens bovids (cattle, goats, sheep, antelopes etc.), and its presence in female varies wildly by species, as does the horn's shape and size. Unlike antlers, they never have branches, and they keep growing for as long as the animal lives. Barring very few exceptions (e.g. four-horned antelope), it's limited to one pair, but the trait of two or more is occasionally seen in the wild.

Certain domesticated breeds have higher likelihood of sporting more than a pair ("polycerate"), or even none. The latter are said to be "polled", which can only be reliably verified by seeing male specimens -- it should be noted that not a single breed (or species, for that matter) has only females presenting horns. As for multiple pairs, sheep present the vast majority of cases, because some breeds have much higher chances of being born with more than one pair (e.g. Navajo-Churro, Hebridean), to the point where it's the norm (e.g. Jacob, Manx Loaghtan), with males having a higher probability. These extra paits have a much higher probability of being asymmetrical.

Of the remaining 3 families, tragulids (mouse-deer a.k.a. chevrotain) and moschids (musk deer) are the odd men out, having foregone any kind of head protrusions completely, developing fangs instead for the purpose of sexual selection. It's a striking sight, given that they're herbivores. The former present fangs in both sexes, and the latter, only on the males.

The odder men out are the water deer, the tufted deer and the muntjac, which present fangs instead of antlers, despite being part of the cervid family. Similar to their antlers' tho, only the males have fangs.

The oddest man out is the sole species in the antilocaprid family, the pronghorn. Both sexes grow true horns like bovids do, yet the keratin layer alone is shed every year and regrown, while the bone core remains, in a weird twist to cervids' antlers.

The man so out it doesn't even count is the horned screamer, which is actually a bird with a single silly-looking, long and spiny "horn" made of pure keratin growing from its forehead, on both sexes. It keeps growing for life, but it's so thin it constantly breaks at the tip, remaining mostly about the same size.