thirty

prose

acidity

sankyoku, a traditional Japanese ensemble consisting of three instruments: shakuhachi, shamisen, and koto (formerly kokyu, shamisen, and koto)

(uncommon) tripod

the three types of arms made out of leather: armor, helmet, and shield / in traditional Japanese cosmology, a general term for the three years that often accompanied change: kakumei, kakuun, and kakurei

coral

acetylsalicylic acid

acetic acid

barbituric acid (the organic acid compound)