題 - topic, subject

environmental problem; environmental issue

example; exercise (for the reader)

title; index; heading; headline; caption

title lettering

abduction issue (esp. of those Japanese abducted by North Korea)

question (e.g. on a test); problem

subject; theme; issue; matter

topic of discussion; agenda

subtitle; subheading

proposition; thesis; notion; theory

difficult problem; challenge

different thing; another question; different case