The phrase "a principal topic of" is correct and usable in written English.
It can be used when discussing the main subject or theme of a discussion, paper, or presentation.
Example: "The research paper focuses on a principal topic of climate change and its impact on global ecosystems."
Alternatives: "a key subject of" or "a main theme of".
A principal topic on the agenda will be removing barriers to trade.
Forty-two of the Senate's 50 Democrats attended a private retreat this weekend in Farmington, Pa., where a principal topic was forging a unified party strategy to combat the White House on judicial nominees.
He knew that the principal topic of conversation would be the Yankees' record of four victories and eleven losses.
Join the discussion.Go to Awards Season Enlarge This Image Marie Rivière/Agence France-Presse — Getty Images Passion was the principal topic of the director Eric Rohmer's films.
The principal topic of conversation is often the speed of the greens, and the closest thing to controversy is the yearly refusal to discuss whether the club will some day include a woman as a member.
Second, Cohen thinks the principal topic of the theory of knowledge is mathematically-precise natural science paradigmatically mathematics and physics (Richardson 2006).
For earlier results on various aspects of solvability theory of boundary value problems and spectral theory in the half line case, the situation closely related to the principal topic of this paper, we refer, for instance, to [7 10].
Putin then announced that Syria would be the principal topic of discussion at the evening's working dinner.
Many contemporary studies of this type [e.g. [ 7- 9]] emphasise the central role of risk assessment and of 'keeping order' in structuring the conduct of mental healthcare, but generally do not focus on safety as their principal topic of interest.
Perhaps, a most illuminating proof of the impossibility of a Dirichlet eigenfunction to be simultaneously a Neumann eigenfunction can be based on the third Green identity, which naturally leads to one of the principal topics of this paper.
