This is the adverb of 'thematic', and it does two jobs. First, it describes HOW something is arranged: 'the poems are grouped thematically' means they are grouped by shared idea — all the poems about the sea together, all the poems about mothers together — rather than by date written or by author. You hear it about libraries, museums, syllabuses, playlists, conference programmes. It answers the question 'by what principle is this ordered?' Second, and just as common, it works as a kind of frame word meaning 'as far as the deep ideas go'. 'Thematically, the film is about forgiveness, but on the surface it's a bank robbery.' 'The two books are thematically linked.' Used this way it usually sits at the start of the sentence or right before a verb like 'linked', 'similar', 'related', and it quietly signals: I am now talking about the underlying meaning, not the plot, not the style, not the pictures. That is a very useful move in essays, because it lets a student compare two very different-looking works honestly. Register: formal to neutral-academic. Extremely common in literature and film writing, and in the language of grant applications and reports ('thematically organised research'). Rare in casual talk, where people say 'in terms of what it's about' or 'idea-wise'.

在主題上、按主題地（副詞）。寫評論或報告時常放句首：「就主題而言…」