Breakdown of Sinceramente, no hables de ese tema.
de
of
no
no / not
hablar
to speak
ese
that (m.sg., also esa, esos, esas, eso)
Questions & Answers about Sinceramente, no hables de ese tema.
How does sinceramente work here, and why is it set off by a comma?
Here, sinceramente acts as a sentence adverb. Instead of describing how an action is performed, it expresses your overall perspective on the sentence, meaning 'To be honest with you...' or 'Speaking honestly...'. When used this way, these adverbs usually go at the beginning of the sentence and are separated by a comma.
Could I move sinceramente to the end of the sentence?
Why is the verb form no hables instead of no hablas?
No hables is the negative command (imperative) for tú. In Spanish, all negative commands must use the present subjunctive form. This is why the -ar verb hablar changes to the -es ending here.
Since tema ends in -a, why do we use the masculine word ese instead of esa?
Tema is a masculine noun, which is why it takes the masculine demonstrative adjective ese. As a quick refresher, many Spanish words that end in -ma and come from Greek are masculine, such as el problema, el sistema, and el idioma.