From heart + felt.

• (RP) IPA: /ˈhɑːt.fɛlt/
• (America) IPA: /ˈhɑːɹt.fɛlt/

heartfelt

1. Believed or felt deeply and sincerely.

   a heartfelt apology

   She expressed her heartfelt sympathies at the death of his mother.

   • 1820, William Hazlitt, “Lecture I. Introductory.”, in Lectures Chiefly on the Dramatic Literature of the Age of Elizabeth. […], London: Stodart and Steuart, […]; Edinburgh: Bell and Bradfute, →OCLC ↗, page 2 ↗:

     [T]hey were not the spoiled children of affectation and refinement, but a bold, vigorous, independent race of thinkers, with prodigious strength and energy, with none but natural grace, and heartfelt unobtrusive delicacy.

• genuine, sincere, true

• French: sincère
• German: herzlich, von Herzen kommend, tief empfunden, innig, aufrecht
• Italian: sentito, sincero
• Portuguese: sincero
• Russian: серде́чный
• Spanish: sentido