words of thanks; acknowledgements
Formal expression of gratitude, often used in speeches, prefaces, or written acknowledgements. Not casual 'thank you'.
卒業式で、彼は指導教員への謝辞を述べた。
At the graduation ceremony, he gave words of thanks to his advisor.
論文
Rare formal use for an apology; more commonly expressed with 謝罪 or お詫び. May appear in older or very formal written contexts.
古い文書では、謝辞が謝罪の意味で使われることがある。
In old documents, 謝辞 is sometimes used to mean an apology.
I include acknowledgements at the end of the thesis.
謝辞 is a speech or words of thanks, while 謝礼 is a monetary or material reward given as thanks, not the words themselves.
Compound of 謝 (thanks, apology) and 辞 (words, speech). The kanji combination naturally yields 'words of thanks' or 'words of apology', with the former being the dominant modern sense.