"Always acknowledge your sources at the end of an essay." — What does it mean?

Question

Cambridge Dictionary explains that there are two meanings of "acknowledge" and gives an example (below).

the first meaning of "acknowledge":

to accept, admit, or recognize something, or the truth or existence of something

the second meaning is:

to tell someone, usually in a letter or email, that you have received something they sent you

This is an example from the block "More examples":

(1) Always acknowledge your sources at the end of an essay.

Based on these two meanings, I couldn't understand what "acknowledge" means in (1).
Could you explain it to me please?

Answer 1

You should admit (to your reader) what your sources are.

Sometimes a dictionary definition is a "gloss", you can just replace the word with the definition and it makes sense. Sometimes the definition is more of an explanation of what a word means.

Well, this definition might not be a straightforward gloss. But this is the purpose of the examples - They let you see how the word could be used in context.

One use of "acknowledge" is in the collocation "acknowledge (ones) sources". It means to write a reference list or bibliography.

An acknowledgement is an act of thanking someone, by making known the good thing that they have done. In an essay you "thank" the people whose book you have read by acknowledging them in the reference list, and making known that you have used their books while writing the essay.

Answer 2

The meaning of the example can be explained by the first definition.

Always acknowledge your sources at the end of an essay.

It means you must say (or inform) which books were used, in other words "the existence of something" and/or acknowledge (recognise) the author of any quotes cited in an essay.