题材
tícái · HSK 5
theme
📚 题 = topic/question + 材 = material → topic-material = subject matter
题 (tí) means topic or question (as in 问题 question, 题目 title); 材 (cái) means material or timber (as in 材料 material). Together 题材 literally stacks topic + material to mean the subject matter or theme of a work.
题 — page radical 頁 + 是 (phonetic)
题 is a phono-semantic compound. The right side 是 gives the sound (shì→tí), while the left 頁 (simplified 页, 'head/page') carries the meaning, since titles and topics were written at the top of a page. Original sense was 'forehead,' later extended to 'title, topic, problem.'