The word 'thematic' is used as an adjective and the meaning that the word conveys is that of something that is connected with the theme of something. The distinct feature of this word is that if you want to use the word, use it only before noun and not otherwise. Following sentence can make you understand the word well as in the sentence the word is being used in the context: The thematic structure of this text is the only thing that should be read to understand it quite well. In the abovementioned sentence it is conveyed that the text that is pertinent to the theme is the only thing useful to understand it well.
The word has its adverbial form also and the adverb that you can use for the word is thematically.
The word has its adverbial form also and the adverb that you can use for the word is thematically.