reference

As a noun directory

is a list of names, addresses etc, of specific classes of people or organizations, often in alphabetical order or in some classification.

As an adjective directory

is containing directions; instructing; directorial.

As a noun associate

is (slang) an associate's degree.

As a noun reference

is a relationship or relation ({{term|to}} something).

As a verb reference

is to refer to, to make reference to, to cite.

As an adjective foundational is

of, or relating to a foundation or foundations.

As a noun comparison is

the act of comparing or the state or process of being compared.

As an initialism doc

is drug of choice.

As a noun resources

is .

As a noun protocol is

.

As a verb protocol is

(obsolete|transitive) to make a protocol of.

Reference is a related term of notice.

As a noun notice is

the act of observing; perception.

As a verb notice is

to observe or take notice of.

As a proper noun monitor is

any of several publications eg the "christian science monitor".

As nouns the difference between reference and sources

is that reference is a relationship or relation ({{term|to}} something) while sources is plural of lang=en.

As verbs the difference between reference and sources

is that reference is to refer to, to make reference to, to cite while sources is third-person singular of source.