#pigment

• Small mole — Diminutive of the noun 'alună' (the hazelnut fruit) or an alternative, sometimes regional or affective, form for 'aluniță' (small pigmented spot on the skin, nevocellular nevus). In a botanical sense, it describes a small, immature, or wild hazelnut, while in an anatomical sense, it represents a small, circumscribed benign cutaneous formation colored in shades of brown or black.
• Amphichromy — A rare biological or chemical phenomenon characterized by the simultaneous or successive appearance of two different colors or shades within the same plant organ, cell, or molecular compound; in botany, it describes the dual chromatic variation of flower petals depending on the maturity stage, light intensity, or pH changes within cellular vacuoles.
• Anthemis tinctoria — The scientific name for golden marguerite or dyer's chamomile, a perennial herbaceous plant in the family Asteraceae. Characterized by entirely yellow flower heads, it was historically used in the textile industry to extract a natural yellow dye and is now valued as an ornamental plant.
• Anti-graying — The act of preventing or halting the process of hair graying or textile chromatic degradation, and its result; an anti-graying action. In the modern cosmetics industry, the term defines the structural function of advanced hair treatments that protect the hair's natural pigments against oxidative stress.
• Anthocyanin — A water-soluble plant pigment belonging to the flavonoid class, present in the cellular vacuoles of many plants, flowers, and fruits (such as blueberries, blackberries, grapes, or red cabbage), responsible for coloring them in intense shades of red, purple, or blue. These compounds alter their color based on the environmental pH and play a major physiological role as powerful antioxidants, protecting plant tissues from ultraviolet radiation and oxidative stress.
• Anthochlor — A water-soluble plant pigment belonging to the flavonoid class (such as chalcones and aurones), found dissolved in the cell vacuoles of certain flowers (such as primroses or dahlias), responsible for coloring them in bright yellow or ivory shades. Unlike carotenoids, which are insoluble plastid pigments, anthochlor turns rapidly to reddish-red in the presence of ammonia or alkaline vapors.
• Anthic substance — An organic substance, plant pigment, or chemical derivative extracted from or structurally correlated with plants of the genus Anthus or specific floral elements; it may also describe a morphological feature or microscopic structural composition presenting affinities with flower biology. In a biochemical sense, it defines a natural compound used in the laboratory for its reactive or spectral coloring properties.
• Anthoxanthin — A water-soluble plant pigment belonging to the flavonoid class, possessing a white, yellowish, or cream color, present in the cellular vacuoles of many plants, flowers, and fruits (such as cauliflower, onions, or white petals). This structural organic compound modifies its spectral hue depending on the acidity of the medium, becoming intense yellow in the presence of alkaline substances, and plays an essential role in protecting plant tissues against ultraviolet radiation and in cellular oxidation processes.
• Anthraquinone — An aromatic diketone structurally derived from anthracene, having the chemical formula C14H8O2, occurring as yellow crystals insoluble in water; a substance obtained through the oxidation of anthracene or via synthesis from phthalic anhydride and benzene. This organic compound functions as a fundamental intermediate in the chemical industry for manufacturing stable anthraquinone dyes, high-quality pigments, and in the industrial production of hydrogen peroxide.
• Anthraquinonic — Belonging to anthraquinone, referring to anthraquinone, or structurally deriving from the core of this aromatic diketone; a chemical compound or plant pigment (such as certain natural derivatives found in medicinal plants or fungi) characterized by the presence of ketone groups fixed onto the three-ring fused system. In an industrial sense, it describes a major class of synthetic dyes renowned for their remarkable lightfastness and high-performance color fixation on textile fibers.
• Copper pigment — An extremely rare technical or mineralogical term, sometimes used to designate an artificial compound or a rare variety of mineral oxide with a granular appearance and an intense copper-like coloration; an experimental shade or pigment used in fine metallurgy.
• Archiochrome — An extremely rare term used in some works on the history of biology or early evolutionary theories to designate a hypothetical primitive biological pigment or the original, ancestral state of coloration of an organism or cellular structure. It represents a structural theoretical concept that attempted to explain the evolution of chromatic systems in nature from simple to complex forms.
• Areola — A small circular area, pigmented or structurally differentiated, surrounding a central point, such as the darker ring of skin around the nipple or the space bounded by the secondary vein ramifications of a leaf. In botany, the term also denotes the microscopic structure or cushion of hairs or spines specific to cacti (Cactaceae family), from which flowers, new branches, or defensive needles develop.
• Argyria — A rare dermatological and toxicological condition caused by prolonged exposure to or chronic ingestion of silver, silver dust, or silver compounds (such as colloidal silver). This structural condition manifests as the irreversible deposition of metallic granules within connective tissues, mucous membranes, and the dermis, leading to a characteristic slate-blue or silvery-gray pigmentation of the skin that intensifies in areas directly exposed to solar radiation.
• Argyria — A rare dermatological and toxicological condition caused by the pathological and irreversible accumulation of elemental silver particles or its compounds within body tissues, resulting from prolonged occupational exposure or chronic ingestion (such as colloidal silver). This condition structurally manifests as a slate-blue or silvery-gray discoloration of the skin, mucous membranes, and nails, which intensifies in areas directly exposed to solar radiation.
• Orpiment — A mineral belonging to the sulfide class, composed of arsenic trisulfide, exhibiting a lemon-yellow or golden-yellow color with a pearly or greasy luster, highly toxic, historically used as a paint pigment and in tanning. In archaeology, it is studied as a major yellow pigment in medieval manuscripts and ancient Egyptian art.
• Azurite — A natural basic copper carbonate mineral with a monoclinic crystal structure, characterized by an intense, glossy, vitreous blue color and a famous chemical instability, often transforming into malachite under the influence of moisture. This structural mineral is found in the oxidation zones of copper ore deposits, historically used as a fine paint pigment and currently as a semi-precious stone for jewelry or decorative objects.
• Bacteriochlorophyll — A tetrapyrrolic photosynthetic pigment, structurally related to the chlorophyll of green plants, present in anoxygenical phototrophic bacteria (such as purple and green sulfur bacteria). Biochemically, bacteriochlorophyll absorbs light in the near-infrared wavelength ranges, allowing photosynthesis to occur without producing oxygen in deep aquatic environments or dark sediments.