Do *Mundi* and *Mundum* mean different things?

These are the exact same word, and yes both mean "world" but no you cannot substitute them for each other.

1. What is the meaning of Mundum?
2. What is the Latin name of Mundi?
3. What is the origin of the word Mundi?

What is the meaning of Mundum?

: against the world : in defiance of all general opinion.

What is the Latin name of Mundi?

Mundi- Sphaeranthus indicus is used in Ayurvedic treatment of pain, localized swelling, indigestion, headache, cough, elephantiasis, goiter, skin diseases and to improve the sexual vigor. Latin Name- Sphaeranthus indicus Linn.

What is the origin of the word Mundi?

anima mundi (n.)

From fem. of Latin animus "the rational soul; life; the mental powers, intelligence" (see animus) + genitive of mundus "universe, world" (see mundane).