The kaffir lime (Citrus hystrix), sometimes referred to in English as the makrut lime or Mauritius papeda, is a fruit native to tropical Asia including India, Nepal, Bangladesh, Thailand, Indonesia, Malaysia and the Philippines.
Citrus hystrix is a thorny bush, 6 to 35 feet (1.8 to 10.7 m) tall, with aromatic and distinctively shaped "double" leaves. The makrut lime is a rough, bumpy green fruit. The green lime fruit is distinguished by its bumpy exterior and its small size (approx. 4 cm (2 in) wide).
The compound responsible for the characteristic aroma was identified as (–)-(S)-citronellal, which is contained in the leaf oil up to 80%; minor components include citronellol (10%), nerol and limonene.