arcane

As a noun cipher

is a numeric character.

As a verb cipher

is (regional|dated) to calculate.

As an adjective arcane is

understood by only a few; obscure; requiring secret or mysterious knowledge.

As adjectives the difference between arcane and eldritch

is that arcane is understood by only a few; obscure; requiring secret or mysterious knowledge while eldritch is unearthly, alien, supernatural, weird, spooky, eerie.

As an adjective arcane

is understood by only a few; obscure; requiring secret or mysterious knowledge.

As a letter x is

the twenty-fourth letter of the.

As a symbol x is

voiceless velar fricative.

As adjectives the difference between esoterica and arcane

is that esoterica is while arcane is understood by only a few; obscure; requiring secret or mysterious knowledge.

As adjectives the difference between convival and arcane

is that convival is (obsolete) relating to a feast or festivity; convivial while arcane is understood by only a few; obscure; requiring secret or mysterious knowledge.

As adjectives the difference between arcane and hermetic

is that arcane is understood by only a few; obscure; requiring secret or mysterious knowledge while hermetic is (chiefly with capital initial) pertaining to (hermes trismegistus) or the writings attributed to him.

As a noun hermetic is

(in plural) hermetic philosophy or practice.

As adjectives the difference between arcane and obsolete

is that arcane is understood by only a few; obscure; requiring secret or mysterious knowledge while obsolete is obsolete, deprecated (computing).

As adjectives the difference between arcane and false

is that arcane is understood by only a few; obscure; requiring secret or mysterious knowledge while false is (label) one of two states of a boolean variable; logic.

As adjectives the difference between arcane and progressive

is that arcane is understood by only a few; obscure; requiring secret or mysterious knowledge while progressive is belonging to or supporting a.

As a noun progressive is

a member or supporter of a.

As adjectives the difference between arcane and undefined

is that arcane is understood by only a few; obscure; requiring secret or mysterious knowledge while undefined is lacking a definition or value.