• 亜細亜あじあ — Asia (classical writing)
• 亜鉛あえん — zinc
• 亜流ありゅう — sub-school; derivative style
• 亜硫酸ありゅうさん — sulfurous acid
• 亜寒帯あかんたい — subarctic zone
• 東亜圏とうあけん — East Asia region
• 白亜はくあの殿堂でんどう — National Diet Building (lit. “white-stone hall”)

亜 originally represented something that comes next to or beneath another. This idea expanded to meanings like “secondary,” “sub-,” and later became a phonetic symbol used in words such as 亜細亜あじあ for Asia.