ledger vs cost ledger

ledger and cost ledger both are nouns.

Word	Noun	Adjective	Verb	Adverb
ledger	Yes	No	No	No
cost ledger	Yes	No	No	No

As nouns, cost ledger is a hyponym of ledger; that is, cost ledger is a word with a more specific, narrower meaning than ledger:

ledger: a record in which commercial accounts are recorded
cost ledger: ledger showing the accumulated costs classified in various ways

Other hyponyms of ledger include general ledger, subsidiary ledger, daybook, journal.

ledger (noun)	cost ledger (noun)
an accounting journal as a physical object	ledger showing the accumulated costs classified in various ways
a record in which commercial accounts are recorded