In Islam, djinn (singular djinnee) are believed to be the equivalent of spirits or demons. They can be good or evil, and are said to live side by side with humans, but are not perceivable by them.
There are also stories about people managing to gain control of djinn, usually through difficult, secret, magical tasks.
... are expressed) are organized into four 'systems' (plus gerunds and infinitives, along with such creatures as intensives[?]/frequentives[?], desideratives[?], ...