alphabet vs rudiments

alphabet and rudiments both are nouns.

Word	Noun	Adjective	Verb	Adverb
alphabet	Yes	No	No	No
rudiments	Yes	No	No	No

As nouns, alphabet and rudiments are synonyms defined as:

alphabet and rudiments: the elementary stages of any subject (usually plural)

Other synonyms of alphabet include first principles.

alphabet (noun)	rudiments (noun)
the elementary stages of any subject (usually plural)	the elementary stages of any subject (usually plural)
a character set that includes letters and is used to write a language	a statement of fundamental facts or principles