معنی کلمه Thesis or dissertation

a long piece of writing on a particular subject, especially one that is done for a higher college or university degree:
a doctoral thesis (= for a PhD)
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C2 formal the main idea, opinion, or theory of a person, group, piece of writing, or speech:
Their main thesis was that war was inevitable.

More examples

I wrote my thesis on literacy strategies for boys.
Her main thesis is that children need a lot of verbal stimulation.

He wrote his Master's dissertation.