topic同义词替换
topic同义词替换词是subject。subject主题，题目，话题，题材，问题，学科，科目，课程，表现。subject的例句It was I who first raised the subject of plastic surgery（是我第一个提到整形手术这个话题的）。
subject的例句Surprisingly，mathematics was voted their favourite subject（令人惊讶的是，数学课被选为他们最喜欢的科目）；Her favourite subjects are shells spotted on beach walks（她最喜爱的题材是那些在海边散步时发现的贝壳）。